Thanks for all the replies. Today, I tried using a heat gun and a hand-held blow torch. No luck. It got very hot, well over the 200 degrees west marine said would soften their epoxy, and it didn't budge! I gave up and am shipping it anyway, so I guess it will all work out.
So, for everyone in the future, epoxy is a permanent fix for a loose boat. Don't expect to ever take it apart.