What is his weight in grams? You say he is in the in between stage. ( which is what mine is in ) that would be the 350 to 500 gram I believe. If he is not 500 grams a small rat might be too big for him. It might not be the idea of it being a rat (but could be) it might be the fact the feeder was just too big as well as the new smell.
I agree with the previous poster, sounds like you are trying too often. I would try every 7 days. If he weighs around 400 grams you might want to try 2 small mice ( totaling 40 or so grams ) Unless you can find a rat size around 40 grams. But that is a hard size to find except maybe on line. Then once your snake gets to 500 grams and over ( which won't take very long ) you can try a small 50 gram rat. Some snakes do get stuck on mice I had one that wouldn't eat rat so I know what you are talking about. But right now I'd say it might have been the size issue and now it's because you are trying too often with the mice.