Getting him to eat anything is what's important now. There's nothing wrong with eating live mice and going to f/t rAts later. Making feeding time a positive experience will help him gain confidence.
How did u offer the live mice? Some snakes want a break between each one, others will eat them right after one another.
I offered him one and it took some coaxing but he took it. Second one he went up to, poked with his nose, and turned away from. I waited almost an hour and stayed with him before I took it out.