Are you monitoring his weight? I wouldn't worry for another month or three unless he's dropping weight fast.

You could keep the whole cage covered in a towel or sheet, too, especially if the snake used to be housed in an opaque tub.

If he was only ever fed live, you could try that. Or do the zombie rat dance with tongs if he's used to moving prey. Use a hairdryer to heat up the head of the thawed rat. I had one that wouldn't switch to thawed prey until I brained the rat - poke a small hole in the skull so they can smell the brain and cerebrospinal fluid.