I think being scared is very normal, in fact if you were all happy and there was no questions that would be more worrisome. I used to think 4 months was a lot, but after reading more on addiction the time frame that would make me feel a bit better would be closer to a year. BUT 4 months if he is in fact a RA, not just not drinking, is a great start. If you feel like it is time to give it a try I would asked yourself how healed you are from having an AH. It is pretty likely that he will at least slip up a few times so how is that going to make you feel? How easy or hard is it for him to move right back out again? If there was physical abuse before that in itself would be a huge warning to maybe rethink this timeline. 4 months of not drinking IMO is not nearly enough if there was abuse in the past.
Decisions are hard, I too am really struggling with what is the best thing to do for my family at this point. We can only do our best, but we need to be educated, healed, and thinking clearly when we do.