My heart goes out to you. Good job. I had virtually the same trailer (2003 Aerolite Cub 236) and the exact same thing happened. The leak was primarily from the front bunk hinge. It rotted all the way back to the bathroom.
Knowing that the floor had luan ply on both sides of the foam that needed replacing or re-engineering with metal floor joists, I decided to cut my losses. Sold it for $2,500 because I knew I'd never get it fixed right.
I'm truly surprised that there hasn't been a class action lawsuit on this flooring design, which is still used today. It works great when new (lite, strong, well insulated). But if you get a minor leak, you are screwed. There's thousands of RV's out there with "spongy floors" because of this poorly executed design and choice of materials. It's made worse by the undercarriage barrier which keeps the moisture in and creates a better environment for rot and mold.
Enjoy your camping trips.
