There are smaller, lighter 5th wheels out there just gotta look around
Air bags on the rear axle of your truck would help.
Some things to help you tow a little more and get a little better fuel economy out of it.
1.) Chip/tuner meant for towing NOT speed performance
2.) Catback exhaust, a Banks Power Pack would be something to really think about.
3.) CA legal Cold Air Intake with a foam cover over your filter (For Off road to keep your filter from clogging early)
4.) Electric Fan if your truck doesnt already have it, find a dual kit that flow at least 5000cfm, a dual speed kit will keep you from running max all the time.
5.) Look into tow kits for your transmission
6.) Run a transmission cooler if you dont have one.
7.) Run an oil cooler if you dont have one.
8.) Look into a Procharger P1SC centrifugal supercharger. The powerband is linear and goes up with engine RPM, it really helps out when towing but works more in the mid to high RPM range, a D1SC would come into boost sooner but it is more expensive. Be sure to run an intercooled version, if you are short on space you can run a Vortech Liquid to Air cooler or go to a Vortech or other Centrifugal system. There are a few to choose from and they are easy to put on for the most part.
9.) Look into upgrading those front brakes, huge for anyone towing.
Its easy to drop a ton of money into your truck but if you do the work yourself, buy quality used parts and research your prices you could get one hell of a tow rig out of your truck and save a little gas doing it because the more power your truck has to tow means less effort is needed to tow the same amount.
I am a Ford guy but it almost all carries over the same to Chevy.