I am cautious in my reply because I believe only you can truly know whether staying is the right thing for you. I will comment on some general points however.

I think a lot depends on what we define as 'happy', that means different things to us all, for sure long term relationships do not have the excitement and hormones that they did in the first few years, that's natural. However contentment can be 'happy' to many, part of that can be satisfaction from the general home and family life, the kids you reared together. I guess for many of us it's that sense of being a 'team', that doesn't mean never having problems, it means both trying to pull in the same direction to overcome them IMO.

I do think there is a lot to be said for making sure your spouse is not everything in your world and making sure there are lots of sources of satisfaction in other areas of your life, be it work, hobbies, volunteering, friends whatever. In my experience that has made me a happier wife and mother.

To be specific to you BM a history of abuse does complicate things, and 2 months in is not long. I'm wondering how you feel about the past abuse, are you feeling safe, healed and do you forgive him?