Hello and welcome to SR! This is a place of great support.
Do you go to any meetings like Alanon or Celebrate Recovery? That would be a great start to face to face support from people who are walking in your same shoes.
I would also say that seeing a counselor who specializes in helping families who deal with addiction would be of great help to you. I am sure you realize, alcoholism is a progressive disease, and unless he gets some sort of control on it, it will progress. It won't be just you that is being exposed to this, but a child. I hate to say, but his X walking out was likely b/c she was at the end of her rope and she had to do it for herself. At least that is what happened to me. I stayed for 18 years. I was miserable and felt like I was going to have a nervous breakdown. It was awful stress for my children. Addiction does truly rip families apart, weather you stay w/him or not. However, it's good that you realize he can only change when HE is ready. And the reality is, that may be never.
I recommend you read all the stickies at the top of the forum. Keep posting, you are not alone. One thing is for sure, you and your baby deserve for you to take good care of yourself!!! That is so important.
One last thing, Congrats to you on fighting your own addiction. You have chosen what is important to you, and you fight for that. That is a wonderful thing for you and your baby.
Many hugs to you.