Skyleh; He may be controlling his drinking for the OW now, but wait till the relationship gets a little longer. Once he has more time in this, his true colours will show.
Just think, then she will be the one in your shoes now. I know its not much comfort for you now, but you do deserve better, and whatever you do don't blame yourself!
A woman once told me during my separation that the best revenge on a husband is to thrive, be happy, and take care of ourselves emotionally and physically. Turned out to be true. When I started dating a man 2 years after leaving my husband of 20 years, it destroyed him, even though he had his OW or a couple OW's at the time.
Take care of yourself, you're worth it.