I'm still trying to answer the question when to leave. It took me a lot of years to understand that the man I'd raised my sons with was gone. My best friend was gone and in his place was this shell of a person with a compromised brain damaged by alcohol. My husband didn't start drinking problematically until we'd been together over 20 years. Our boys were in their late teens. They are all grown up now.
What about your son? What is his father's drinking doing to him?
I'm currently putting together a plan to leave. I've collected and copied important documents. I'm stashing cash. I have it all hidden in a safe place. I'll be starting financial research this week (that ought to take about 10 minutes). Anyway, when the day comes that I choose to leave, I'll be able to pick up and be out of here in a few minutes.
I'm at the point where I don't know if I'll miss my husband much or at all. But I really don't want to walk away from my garden, my kitchen, my sewing room. I know. I know that's all stuff but not really. I'm at my best in my garden and my kitchen.
I assume your husband isn't physically abusive. My husband isn't either but often (not always) when he drinks he has a nasty mouth. When he sobers-up and sweetens-up, I'd say to myself "well, he doesn't really mean to talk like that." Now I think "He doesn't mean it but by golly he does it and I deserve better".
I wonder why should I leave? Why can't he? Hmmm. I need to figure out how to get that to happen.
There are plenty of checklists on line so you can plan how to get out of your situation. There are some good links at the top of the Friends/Family of Alcoholics forum in the "sticky" section.