Actually snake mites are not indigenous, so I'm assuming he's not a wild caught snake, unless he caught them while captive in someone's snake collection.

A snake that is so weak that "it doesn't really move" is probably on death's door...sorry to say. So whatever you're doing, if you hope to save him, had better
be quick. And just because a snake has mites, does NOT mean that he doesn't ALSO have internal parasites. Saving this snake will take some meds, IMO.