To address you points on the damage capability of the Sweet Commadners I wasn't downplaying them, but how often would BM be sending her children to randomly wreck islands? Unlike Kaidou's crew, BM 's crew is very ordered. They pretty much chill at Whole Cake Island managing their respective towns until BM tells them to go crush someone who slighted her. Meanwhile, with the Best Pirates you get the reckless Jack and the mentally unstable Pleasures who would randomly attack islands for the sake of it.
Think back to when we first saw X Drake in the New World, someone from the Beast Pirates had went out and claimed that land. Meanwhile, BM seems to rarely claim land outside of Whole Cake Island. Even BM's temporary ownership over Fishman Island was due to Jinbei seeking her out to protect Fishman Island.
So, as for potential threat to the world government the calamities are much more likely to go around causing damage than the sweet commanders, who only seem to act when someone slights BM in some way (i.e. people not coming to the Tea Party, antagonizing her [some of the supernova], or stealing from her [Doflamingo]). Thus, the calamities would be perceived to be more of a threat in that sense.
Now, let's think about the gaping difference between Cracker and Katakuri, which we then should be able to apply to Jack and Katakuri later on.
Cracker as a Sweet Commander is rightly very formidable. At base his Cracker soldiers seem to be an entire tier above Urouge and Snack. Urouge couldn't even chip it and the same goes for Gear 3rd Luffy. They were doing absolutely zero damage and Cracker was actually dominating Gear 3rd Luffy. When Luffy used G4 Boundman against Cracker's biscuit soldier it was pretty much a war of attrition at that point. G4 Boundman wasn't fast enough to deal with Cracker's ability to continuously produce more biscuit soldiers. However, the biscuit soldiers that Luffy made contact with were very easily demolished. Cracker however has a pretty big weakness to water(moisture?) so Nami producing rain and Luffy's ability to eat unfathomable amounts of food allowed the fight to continue even when Luffy ran out of G4.
Eventually, Luffy regained G4 and Cracker was getting tired of the never-ending cycle of creating biscuit soldiers only to have them rained on and eaten. So, Cracker gets out of his biscuit soldier and takes Luffy head-on. Their speed is for the most part pretty comparable and earlier in the fight Cracker was able to cut G4 Boundman with his sword pretzel (by surprise), so offensively he was somewhat of a threat as well. However, Cracker was completely nullified by G4 Stuffed Tankman and one shot, by what I will assume was the Tankman version of King Kong Gun (i.e. the finisher for Tankman like Black mamba is for Snakeman).
Now, this same Luffy who had pretty comparable speed with Cracker himself, was completely capable of tearing through Cracker's maximum defense in the form of his biscuit soldiers, but was unable to outspeed the pace at which Cracker could produce said biscuits went on to fight Katakuri in pretty much the same state. Before Luffy started to learn future sight against Katakuri, there was literally a zero percent chance Luffy could've won that fight. Katakuri with Power Mochi was able to match G4 Boundman's strength with zero issue, Katakuri's speed was even outspeeding Snakeman for a while. And there is a point in the fight where Katakuri was able to completely dodge(phase through might be more accurate?) a barrage of punches from G4 Boundman. Luffy before learning future sight might as well been fodder. Not to mention the awakening which Luffy also had zero chance against.
Katakuri stomps Cracker with no issues. Strength-wise with power mochi Katakuri would be capable of breaking through Cracker's biscuit soldiers. Speed-wise he is vastly superior in both reaction time and actual overall speed. Luffy who before learning future sight had comparable speed to Cracker (some might say even better speed) and before beginning to learn future sight Luffy had no chance of even touching Katakuri (even with G4 Boundman) while Katakuri was able to maintain future sight (i.e. stay calm).
Not to mention the fact Katakuri's awakening would vastly improve his odds being that'd he'd be able to stick the biscuit soldiers in place to easily get at Cracker.
There is an immense gap between Cracker and Katakuri's battle prowess even though to someone like Lucci back in Enies Lobby they are both absolutely overwhelming monsters. Katakuri would sweep Cracker with no issues the same way he one-sidedly destroyed Luffy during the first half of their fight.
[There are other tactics available to Katakuri as well. Peerless donuts allows for greater and more versatile range than Luffy applied during the Cracker fight, and buzzcut mochi seems to be at least around the level of things like Black Mamba or even KKG.]
Now, let's go back to Jack, now that we've hopefully established Cracker gets absolutely trounced by Katakuri.
Jack was tied for the 3rd best stamina feat-wise and some absolutely insane defense when he first debuted. He went 5 days without rest back to back with Inu and Neko. However, not once during that long encounter did Jack deal any meaningful damage to Inu and Neko until he made use of Cesar's poison gas rendering Inu and Neko unable to fight. This speaks to either Jack's attack potency or Inu and Neko's defensive capability. Then in Wano we see Jack get wounded by Ashura Doji. While this doesn't indicate Ashura Doji is just miles better than Jack or anything, it does however set a precedent for his defense being breached.
Ashura Doji I wouldn't rate any higher than 2nd commander and honestly I place him around Jack (3rd commander level) personally. Jack traded pretty mcuh on the spot and was able to deal damage to Ashura Doji as well. Now, obviously a clash isn't the same thing as a full-on battle (otherwise Doflamingo and Aokiji would be equals), but this is telling. There was no real context in the scene making either one of them to be superior than the other.
Going back to Inu and Neko they were both fighting Jack, a 3rd commander, pretty evenly (even though the did were able to rest) and we know from Carrot's comment back in WCI they both have Sulong forms as well that would increase their power.
We have the comment made by Carrot making Inu and Shutenmaru out to seemingly be equals. Granted it's not like Carrot would know the full potential of Shutenmaru, but at least we have some idea that Shutenmaru is somehwat relative to Inu someone who was fighting on par with Jack earlier (granted with rest periods).
Now we even have more context on the Oden and Shutenmaru fight. While Oden it did take a lot of effort to quell Kuri that wasn't only because of Shutenmaru, but he quelled/defeated the entirety of Kuri who dared to challenge him on top of fighting Shutenmaru.
So far there is nothing to suggest or hint that Shutenmaru might be on par with 1st commanders (like Katakuri), so while we don't know exactly where Shutenmaru falls (2nd commander, 3rd commander, or somewhere in between) we do likely know he shouldn't be much if any better than a 2nd commander.
1st commanders are monsters among beasts. Marco is out there taking several admiral attacks including one named attack, Ben Beckman gets some pretty crazy wank from Oda as well as Kizaru to some degree. Katakuri, who we've already deconstructed somewhat. And then King who while we don't have any meaningful information on fights, King alone was enough to ward off the small BM group consisting of: Smoothie, Perospero, and Daifuku (some others as well just less important).
The goal of the above was to hopefully establish Shutenmaru should be considered no higher than 2nd commander (probably around 3rd commander imo) and he was actually able to injure Jack. We don't know much about Shutenmaru's speed, but I think it's safe to say Katakuri is vastly superior in that department.
Jack isn't particularly fast. In fact, during what we got to see of his battle with Neko, Neko was able to give multiple (a few) attacks for every one that Jack dished out. So, already we have someone outspeeding Jack. We have Inu who was going blow for blow and Shutenmaru who was actually able to trade damage with Jack. And there is currently no reason to believe any of them have speed comparable to Katakuri (the man who was completely capable of phasing through a barrage of G4 Boundman punches as well as even outspeed Snakeman for a little while.)
It'd be another thing if Jack had comparable defense to someone like Quee, who was taking hits from an albeit nerfed BM with no haki very well. Those same nerfed attacks from BM were almost able to one shot Hyogoro while he was using advanced armament (though he is old) but Luffy survived it in base. Regardless, that is a full-fledged yonkou's presumably unbridled physical strength. Queen took those hits with no real issue defensively speaking. Of course he realized he couldn't go head-to-head with her even in this nerfed state, so he devised a different solution.
If Jack had that kind of defense, insane attack power, or enough speed/observation haki to not get laughably outsped by a serious Katakuri, I could see Jack being somewhat close to Katakuri. But, he has none of those things: he was seemingly slower than Neko (not terribly, but still), he got damaged by Ashura Doji (someone who shouldn't be any higher than a 2nd commander from what we know so far), and he wasn't able to deal any meaningful damage to Neko or Inu when they were fighting.
Meanwhile, Katakuri has some insane speed and is unlikely to even get touched by any of Jack's attacks, he has things like Buzzcut Mochi as well as his trident to deal significant damage, and as for defense, his immense speed does that for him. Not getting hit in the first place is his defense.
If you have some other analysis for Jack being even close to Katakuri I'm all ears. And for clarity's sake I am referring to this statement you made: "Jack does have a higher bounty than Smoothie which means he is considered a bigger threat than her and since I haven't really seen a difference in strength between Big Mom's and Kaido's cannon fodder I see that as evidence of Jack being stronger than Smoothie and Cracker but weaker than Katakuri."
He's not even close to Katakuri. It's hard to say for Smoothie because we've seen so little of her actual abilities. But, personally (not really part of an analysis) I think she'd at least be able capable of doing what Shutenmaru did to Jack if not more.
Tbh, I don't know who would win against Cracker and Jack, but I'd bet on Jack due to the fact defensively Jack shouldn't have much of an issue against Cracker's biscuit soldiers. Those biscuit soldiers on their own didn't even have a remote chance of injuring G4 Boundman Luffy. While Jack is slower than Neko, being able to trade with Inu and Shutenmaru indicates he isn't an absolute snail. If Cracker ever decided to attack Jack outright (after a long war of attrition), I'd say Jack has the offensive power to take the win at that point. Of course, the most important trait when battling Cracker is either the ability to render his biscuit soldiers immobile/useless with something like a awakening or to outlast Cracker. Given Jack's stamina I'd say he could do that.
However, when considering Smoothie vs. Jack. Jack definitely isn't impenetrable defensively. Shutenmaru was able to breech his defenses and Smoothie who seems to specialize in overwhelming attack (as opposed to something like defense) I expect to also be capable of. At this point Jack's amazing stamina isn't really relevant if he's actually fighting someone who is going to be dealing constant damage to him. As opposed to Neko and Inu back in Zou who dealt no serious damage to Jack over the course of those 5 days. Smoothie vs. Jack probably wouldn't be a sweep (unlike Katakuri vs. Jack), but I would definitely give Smoothie the edge.