Hi,
Couple of things jump out from your post.
Try raising his humidity - what kind of enclosure are you using and can you get us some pics?
Also, try feeding him in his enclosure. Defrost the mouse close by so he can smell dinner is in the air and then heat the head of it up wih a hair drier just before offering it about 3 inches from his head.
There are a few more things but I'd like to see the pics of the enclosure first.
dr del