Well that Kitty Cat should not have needed any work done to it until well after 250,000 miles! Then just injectors and valve adjustment. Now knowing that you had someone work on the engine, I think I would be contacting them and see if they will pay for at least part of the repair bill. Trans bolts do not come out unless someone did not torque them to the correct specs.
You do know a fully loaded Ram 3500 DRW Crew Cab 4X4 Laramie Limited has a payload of 5,432# tow rating of 28,750# and a GCVW rating of 37,500# pounds right? Now will it tow as stable as your unit at the max limits? No but towing 14,400# would not be an issue for it whatsoever. With what you have invested in your FL70? you could have bought a brand new truck without any worries. But with what you have done to it she should run 500K without blinking an eye.
Good luck and happy camping. Don