2013 Keystone Bullet Premier Ultra Light 22RBPR
GVWR (lbs/kgs) 6500 / 2948.4
Yeah, your Jimmy is maxed out when that trailer is wet and loaded for a camping trip.
The shorter wheelbase will weigh less than the longer wheelbase, so it will require slightly less power to climb hills and mountain passes when towing. But that's minor stuff. Your best bet is to replace the ring gear and pinion in your differential(s) with shorter legs. I would go for at least 25% gain in axle ratio to give you adequate towing power. IOW, if your axle ratio is now 3.30. then 3.30 + 25% would be 4.125. 4.10 and 4.11 are cpmmonally available gear ratios, so that's what I'd want.
If you're buying a new tow vehicle, then get it with enough power and torque to get the job done, along with the heaviest duty axle ratio they offer.