What TT can I pull with my Durango??

assuming you will add 1500 lbs. of "stuff" that leaves about 4700 pounds wet. to allow some safety 4500 lbs. should give you a pretty good assortment to choose from. an ascend A231BH has bunks, queen, dinette and is probably under 4,000 lbs. no rubber/TPO roof.
no slide however. don't let the naysayers say you need a F550 to pull it. I pull my Ascend A17RD with my Highlander rated for 5,000 lbs.
bumpy

Look on the driver's side door pillar for the Payload weight rating, something like, "weight of passengers and cargo should not exceed..." The payload weight will be the limiting factor for towing, you will run out of payload weight before you hit the GCWR of the Durango.

not much, 6200 pounds is light, I would go with a tent trailer and be done with it till you need a new truck. A V6 isn't much power to pull a full size front down the road.

My Skyline Eco Camp 20BH is 3600lbs dry with bunks and slide. Your 6200 lbs capacity has to include all the extras which most people estimate to 500lbs but then revise to 1000lbs when they come across a scale.

I had an Acura MDX rated for 5000lbs before and I never even tried to tow with it.