Welcome to the forum. There are a couple good discussion threads on this subject, definitely worth a walk through them. The best way to know your exact towing capacity is to enter the VIN of the vehicle into RAM's towing site. Note this is for factory set up and includes fuel, but if there are any non-factory options, that impacts final numbers. Just a generic look at your option above it would appear your set up in 1500 would have a payload capacity of 1800, and running a 8900# trailer with average of 15% tongue weight would leave 465 pounds for people, hitch, and other incidentals.
Among many issues, putting too much weight on back may not be able to be resolved by a weight distribution hitch, which then takes weight off front. You may read about airbags but they have no impact on weight distribution, they only level the ride. Your front wheels provide all steering and a majority of vehicle braking. So you want to have your rig properly weighted per axle and overall have the right tow vehicle. 2500 or even 3500 single rear wheel can be a great option for you, I have read the 3500 rides a bit better due to rear set up but I never noticed it in my experience and I just replaced a 2500 with a new 2500, ride is great. Gas mileage, I was 15-17 in old one, new one is a little less but I have not really driven enough to get a true comparison yet.
Good luck in your purchase and travels.