I don't think this is the issue since he said the Jeep used to drive fine. That being said it doesn't take long to put an Wixey angle gauge on the Cs and check them. I think there's a flat spot on the bottom if I remember correctly.A go-pro won't show caster issues, nothing need be loose -- DW from caster is just physics
I agree it's VERY unlikely but if the axle was built on a Friday afternoon it's possible one inner C is several degrees off from the other.
Seriously, we're down the list to the "very unlikely" items so it'd be remiss to not at least CHECK. It is difficult to find a good place on each knuckle but I'd try.
The theory being if caster is being measured at the flat on the pumpkin that doesn't mean each inner C is inline with where it should be.
I know it sounds laughable but this is something non-invasive that can be verified solely from LOOKING and MEASURING. No parts need be removed and no wrenches need be abused. NOW, if an initial inspection lead me to believe something was amiss left to right I'd absolutely be dropping the knuckles and putting a straight edge in the bores of the inner C's and checking that with an angle finder.
I hope I'm wrong but I thought OP started the thread for "thinking outside the box" suggestions......well, here's one and it won't cost you a dime or a single aftermarket part.
As Sean said, I'm sure a delta of 1 degree is no big deal. 2? Probably ok. At 3 I'd be concerned 'cause you could have one wheel at 6.2 and the other at 3.2
Again, just a WILD idea that's probably a wild goose chase but FREE to inspect.