It's quite a psychological shift from always drunk to always sober and his life may very well depend on him staying sober.
The fun loving guy may still be in there somewhere but it will be awkward for him to try to feel "normal" when he is going through this phase.
I'm glad you are here and hope you can take good care of yourself and lots of time before you plan any kind of a future with a man who needs to focus on one day at a time.
Good luck, prayers out that he can stay sober.