Hi,
It looks like a bit of scale damage - it should get better with every shed.
You could try feeding him in his enclosure and see if he eats more regularly for you that way? Just make sure theyre are nice open "kill zones" in from of the entrances to his hides so he can strike from cover.
If you can defrost your own dinner without killing yourself you should be fine defrosting rodents - just remember to make sure it is fully defrosted but not to leave it too long and never, ever, under any circumstances, try and microwave them. They can explode
Then heat the head of them up with a hairdrier just before offering so it is a nice big heat signature for him. This is actually worth trying at the moment - he might surprise you and take it.
If you decide to defrost in hot water make sure it is not so hot that it actually cooks the outside of the rodent as this can cause it to split - really not a fun thing.
dr del