I grew up with an alcoholic Father, many people here did have at least one alcoholic parent.
My Mother stayed for 20 years before divorcing him.
When you mention you are wanting your son to have his Father, is this version of your Husband the one you want for him? If not, then it's really just kind of wishful thinking?
In fact, your Son only seeing him for visitation, supervised, would probably be doing them both a favour for their relationship. He will only see his Dad for short periods of time, initially, where, hopefully his Dad can curb his generally terrible behaviour.
Changing him isn't in your control (at all), getting the peace you want for you and your Son is in your control and maybe, just maybe, in the course of that it will salvage whatever relationship they can have.