I have gotten some pretty stubborn snakes to eat. I think one of your problems might be that you move him to eat. First you handle him by putting him in a deli cup, then you are sticking the food item with him, where he knows he cannot get away from it, if need be.
Basically he is stressed and doesn't feel safe. He will not eat unless he feels safe, I've always found that to be a big factor.
I would leave him alone for a few days, no trying to feed, esp. not assist feed. After that wait for a time when he is in his hide, in the evening before he starts cruising. Then put a live rat fuzzy or pup in the opening of his hide and LEAVE. Let him find his food and eat where he feels safe. Make sure there are no distractions.
About not wanting to feed live, I understand. But right now its about the snake, you got him and you are responsible for him. You have to do what is right for him, he can't do it for himself. Hopefully, once he is eating well, you can work on switching him back to F/T.
Good luck !