What hitch do you have?
That is a hell of a lot of weight for a SRW, what are your LOADED weights?
Your trailer suspension most likely has nothing to do with chucking.
Truck "SQUATS" ??? Does it look like this from the side? Or is the rear lower?
Have you towed this RV before the lift with this truck?
17.5" tires on the RV correct? What air pressure are you running?
This is what a loaded truck should look like. This is NOT squat.