If you can answer the following questions it'll help us help you.

What size prey are you offering?
How often are you offering?
Are you handling the snake at all?
How are you heating the prey (if F/T)?


Also, you want to be consistent with what prey you offer and how you offer. You're all over the place trying different things and thats not helping.
Simply feed INSIDE the enclosure. Don't bother with trying all the other stuff.