All measurements were up front. I think that an alignment shop is definitely the way to go at this point.I think you are measuring the rear pinion angle? If so great just buy som upper or lower adj arms and match that number at the transfer case to avoid rear vibes. If the ds angle at the transfer is over 10* you’ll need a rear dc shaft.
As for the caster just go get an alignment as it sits now. You can’t measure off the rad arm mount. You can get close my taking an angle at the knuckle top and bottom studs but the real number comes from the caster sweep from the alignment machine.
At this point you might want to start a dedicated thread to your situation.