Keep praying for him and letting him know on occassion that you are. That meant something to him and that is how you show him that you care.
You can't stop him from doing what he is doing, but you can continue the prayers so that he can see what he is doing.
I feel for him because of the bondage that he is under. I might recommend that you bind the spirit of depression and alcohol from him. Keep praying that every day. Pray that every time he goes to take a drink that it makes him sick before he even drinks it and believe that the Lord is going to do it.
Satan is trying really hard to destroy him. He can't get to you, so he is going to go after your husband. You are is pillar right now and you must be strong for him. He is going to tire of this woman because he is going to see her for what she truly is to him and the Lord is starting to show him. Keep praying that his spiritual eyes will continue to open.
The Lord is working on him and he needs your strength to get through this. You can not go through this for him, but you can certainly pray that the Lord protects him. Put the armor of God around you, him and your son every day.