Need help after a not so great inspection

I would take it to a commercial frame and axle shop and get another opinion. You do not have to get axles from the rv manufacturer. There are generally two are two main axle manufacturing companies : Dexter and Alko. A properly rated axle from any of these would likely fit your frame. Again, I would get another opinion from a shop that specializes I'm frame/axle repair and fabrication.
Before you put a lot more money into it, make sure it is
worth the investment. Steve