This is what I would do if he was mine. If he was eating rats I'd stick with rats, not mice. I always switch over to rats ASAP. Unless you plan on feeding mice forever it is easier to start with rats while young than to try to switch later. Cover the sides and back of his tank, it will help him feel more secure. Don't handle at all until he is feeding consistently. Feed in the evening. I feed around 8 or 9pm, since doing this they eat much more consistently, I've also switched to tubs and they seem to eat better since doing this. I think they just feel more secure and it is easier to maintain temp and humidity in the tubs. Heat the rodents up with a hairdryer. If he doesn't strike leave the rodent in overnight. Some snakes will eat overnight if you leave it in there, some won't.