I am so sorry for what happened. I know that this must be a very painful time for you. It is almost like your husband had this checklist--get married, have a child, and the child is more of a trigger for him. It is as if the responsibility for that child is just going to keep him where he is functioning so much to keep a job. But let's face the truth. It is an addiction. It can get worse.
With taking care of a baby, there is no room for highly functioning father who is drinking on the side. Slow down and look at your options to get out of this situation--do you have family or friends who can help you with taking care of your child?
With an alcoholic, I could never really tell who he really was. The Getting Them Sober books were good just to learn about setting better boundaries. It helped to get involved with Divorce Care at a local church. There were some good Divorced Mom Facebook groups. And it was good to get involved in a local single parent meetup.com group.
It takes time to get over someone. That was 15 years with you being together. Take time for yourself to look about what you want in your life.
What do you really want five years from now? Have confidence in yourself. You are not invisible.