This is a tough one. We had a 5th wheel for quite a while and experienced a lot of what you're going through. I talked directly with the factory and it was a horrible experience. They have fix/excuse for everything. I feel for you. Hopefully every thing can be fixed and you can move on. I didn't deal with Forest River it was Keystone. There was no way they were taking anything back. We eventually sold it, but the list of repairs was ungodly: Heater, Inverter, breakers, breaker box, A/C, trim, molding, axels, etc. Most of the repairs took multiple trips to get it right. Good Luck.
2015 Georgetown Forest River 351DS MH
2008 Keystone Cougar 293SAB 5th Wheel
2007 Jay Flight 30.5RLS 5th Wheel
2006 Jay Flight 29BHS TT