We restored our 25ft. 1990 classic. After looking at your pictures I would advise you to rip your walls back to the inner fiberglass. Then use bondo to seal any pinpoint holes you can't even see. A good respirator is needed. Use rustoleum on all rusty steel. Use heavy duty liquid nails to put your wall layers together. Make paper patterns if necessary. Your walls may be weak all stripped out. Use bracing on the inside. Liquid Nails is cheapest at Walmart. If my memory serves me correctly we used at least one tube on each 4x8 sheet of paneling. Spread in a generous s pattern. May have used more. Roof and window leaks cause this kind of water damage. Keep us posted.