Welcome to FiberglassRV William! You're a lucky fella. Most of us had to BUY our trailers
Fiberglass IS brittle. With enough stress it will chip or crack. A bit of movement on a fiberglass wall is expected... if you push on it. If you have a fiberglass shower in your home, push on a wall and see what happens. It's a non-issue. Your next questions will be how to "revive" the gel coat and for that I'd suggest you use the fabulous search function for words such as waxes or paint
It's possible the strap you're talking about could be used for either the door or the body. Have you checked the body bolts? When you removed the strap, did the door automatically open?
I'd suggest using the Problem Solving forum for questions/problems. It's best to put one question/problem in a single topic.
Don't cry, be happy!