Really what can you say? I am guessing you have had the conversations about how bad it is for him, for you, for your Son and for the family in general.
How alcoholism is progressive and it's not going anywhere good.
Above all I'm sure you have read that you didn't Cause it, can't Control it and can't Cure it. These things are true. What you would like and what he is willing to do may well be two different things. Your choices then become remaining in the relationship with an addict or leaving, there is no inbetween.
That is, of course, your decision and I'm glad you have so much support and have started posting. The bottom line is, what is your boundary? Do you have one?