First thing I'd do is definitely switch to ft so it won't be an issue to keep bulk appropriate sized rats in the freezer. It being that small will be much easier to switch than waiting another year. I have never had issues switching a baby that small so if you want to share exactly how you've gone about trying then maybe I can give more tips. The only snake I have had issues switching is a pied I bought that had been on live until she was an adult so it's taken me another 2 years to get her to take frozen. Another part of the problem that you'll want to avoid with staying on mice, many of them will want to eat 1 and then not take another so growth will be next to nothing after a while so it's worth it to get them switched to rats so the 1 meal they take is an appropriate size.