Hi,
The others have asked most of the good questions so I'll just suggest finding a way to avoid the night time drop if possible.
The specifics of the tank already asked for should let us work out how to best do that if you need help I think.
I'll also throw in the idea of using a hairdrier to heat up the head off the mouse just before offering.
If you can ask the shop you got it from how they prepare and presented the prey when he ate for them - it could be as simple as he doesn't like wet mice.
dr del