First welcome to SR!!
There is alot you can do...for you. You can get educated about alcoholism and the effect it can have on your son and your family. You can learn about what you do and do not have control over. You can learn to be supportive without giving in to the urge to try to fix it.
He is an adult who is concerned about his own drinking. He needs to be the one to call the shots about what he will do about it.
Make yourself at home!
Hugs,
JT