I'm sure he may be fighting a little, as some do. Others just go off by themselves under a rock, and do their thing. As far as the sand, all of mine have at one time or another licked at the sand like they have found a goodie. Even looked as if they ate some tiny grain or pebble. And the skin thing, probably just messing with it, tongue, here and there, some reptiles, and anphibians, eat their shed skin for nutrients. But collareds, just ignore it for the most part.
All sounds pretty much normal. He should not starve, as lights start to go out, after he has been NOT fed and has emptied his tummy, for a bout 7 days, his matabolism will drop, he will sleep and not burn fat.
Remember to hydrate(provide water) while in brumation. And IF you do see that your guy is losing alot of weight, Stop brumation. Have a good weekend,
Eve