Being directly into the fiberglass, I personally wouldn't put any heat at all to it.

How'd it get bent like that?

How long can the deck support sit out of the boat without warping the deck?

What? Are you talking about removing the bulkhead to get into the bow?  You can always cut an access through the center of the bulkhead if there is not one already.  Almost every hull I've seen has access through the front bulkhead, removing the foam is a pain anyway you go at it.  Just start cutting your way through it when you are ready to swap the bow eye.  Like GT said, you are not going to straighten this thing.  While you are in there you should consider creating a backing plate to support the new bow eye just in case.