Hello Seeking help,
No matter how drunk he was, there was a choice in who he contacted and deciding to do it. Since he already puts his drinking above his marriage, he could be perceived on cheating on you with that too.
You are asking what to do. But you put this in context that you take your vows seriously.
Have you ever sat down and wrote out a timeline of your marriage? Write down every fight about his drinking? Every Separation? Any DUIs? Strange job losses? Missing money? Weird things you know an alcoholic haze might have caused. Write it all down. It might be overwhelming to see it on paper. You say you’ve taken refuge at your mom’s before, so be honest with yourself.
Do you have a job? Do you have your own bank account?
I had a bit of a rage when I finally started honestly looking at what a patsy I was. I also recommend running.
These are all things you can do to work on you. Work on you.