Clearly I'm in waaaay over my head here. Spoke to someone over at the Ford dealership today who was really knowledgable. He was able to explain the various weight ratings of the truck and the how and why behind those numbers in a way even I could understand. The only one who's a bigger idiot than my cousin is me for listening to him. I guess I just really wanted to believe my truck could do anything. I thought it was all about power, I understood nothing about payload and axle weight ratings.
No matter what this will cost me big time. The RV dealer is willing to work with me and take the camper back, if that's what I want to do. Still a bad deal though, I'll get a smaller cheaper camper without paying extra. Or I may trade in for a bigger truck. Either way, I clearly have MUCH to learn before I make a decision. I appreciate everyones help.