When he refuses the f/t do you offer live after? I've read many posts advising against this. If you hold him off on food then maybe he'll get hungry enough to go for the f/t. And feeding him live after the f/t does nothing for training him to get off live prey.

This may be a dumb question but are you heating up the f/t mouse at all after it thaws? Blasting the prey with a hair dryer or hot tap water really increases my snake's feeding response. In fact, every time she has refused food she'll nail it once I give it a little warm up.