From a moral point of view, I think you have a good arguement. From a legal point of view, probably not so much. I believe when you signed that as-is agreement. You don't have much of a legal argument.
Sorry it happened to you.
As a side note ford front brakes are famous for locking up. Something about they used a ceramic piston, rather than steel. and overheating the brakes, and disuse contributes, So that is not a surprise. On a 10 year old MH. Hard to blame the dealer for that.
And 6 or 7 hundred pounds, at least you say? in the cabover? while going down the road? that is a huge load. That would be extremely hard on any overhead. I would never get over maybe 150 or so, while driving.