The batteries are fine. The C rating shows how many amps the batteries can tolerate. You won't be close to the limit on either, so you're good.
The velcro might pull a chunk of foam off with it. If the box closes over the foam pieces, just don't tape them. Woodworkers glue won't hurt the foam though so try it if you want.
A little packing tape will help protect the foam. When you do break it, white Elmer's glue will stick it right back together.