Bud,
I've removed the plywood from under and behind the toilet after using a hammer and chisel to remove some plastic placed by a previous owner, only to find that the original plywood is saturated with water and delaminating. I've removed the plywood and called a local shipwright to get new pieces made.
As for the bulkhead there is light damage done to the ply near the bottom six inches, would an injection of epoxy be able to save the bulkhead after drying out the plywood? The bulkhead in question is the one behind the bookshelf and compression post.