I think alot of us on here don't have the issue of the alcoholic spouse so I for one don't know what kind of advice to give. I know that Al Anon is supposed to be really good for dealing with issues for people dealing with alcoholism.
On a different note, I have been in my sitch for about 3 years and living separately for about 8 months so I get not giving up. I don't know if dealing with an alcoholic changes things but it wasn't until my 180's and GAL that my situation started making progress.
Maybe try attending thoses meetings more regularly. Not only will you learn more about the issues you are facing, you will also be meeting new people and socializing.
Keep your head up for both you and your son. Eventually he may say something to her about not seeing her much. It won't mean anything coming from you but if/when he says it she may get it. I know you are really concerned about your son, but you can only control you and your relationship with him.
M 48 H 50 M 25 T 27 D 20,18,15 6/11 H filed 3/12 H dropped 4/12 H moved out