curb weight is right at 4000lbs+- empty. + the 3500lbs of car = 7500lbs.
the truck is 6000lbs+- tuck should tow 6000lbs with 3.2 or 3.5 gears and 7000lbs with 4.10... your above what the truck can tow safely.

Sail factor... head wind with trailer add 2000lbs to 3000lbs to what your towing.

lift bag just keep the back end level, they do nothing to help move or stop anything...

Think safety first... it not only your safety but those who share the road with you...