When I thaw my rats in water I make sure it's never too hot as to cook the rat, if my hand can stand the temperature then it's good. They might be exploding because they have been in the freezer for too long or defrosted improperly.

You should also be feeding your snake a food item about the size of the thickest part of its body one a week, babies can be fed a little more frequently. I wouldn't worry about the snake pooping, they will do their business when they need to.