Mel, welcome to SR. I think you have taken a great step by reaching out for help as you are among people that understand. I am so sorry for the anguish you are going through and I know how hard it is to make a decision. I realized in my situation I lost myself. I am working hard on finding me and becoming self-centered for the first time in my life because what good am I to my kids if I am upset, depressed, and obsessing about the alcoholic?
This part of your post struck me:
I think I would have already called it quits if it were not for our son.... he loves both his parents so much and I don't want to give him a broken home... I also know that if I did call it quits, I could not leave him with my wife.... she is a great mom when she is sober, but when she is drinking she just isn't capable of taking care of him...and it is not safe to leave him with her alone.
As gently as I can say this, your son already has a broken home. The good news is he has YOU! You will find your way, find your strength, and find serenity. Please keep coming back.