Bulkheads - Fixed or Non fixed ?

[S/V AMITY]

My take on your questions:

1. The P365 has a tendency for delamination in the deck? Could the wood core and fiberglass top and bottom layers be rubbing within the deck itself? Is this even possible?
 
      I'd say no.  If your deck was delaminated you'd feel it when you walked on it.

2. There is a gap between the deck and the headliner that would/could cause rubbing while each flex from movement, stress, or temperature?

      No.  I still think its your cabin top moving up.  Can't stress enough... check that tension rod.  I need the beer.