Sorry to read what a tough time you're having seasider. I hope the discussion with your GP is helpful. I'm surprised that a counsellor would make suggestions about the advice you would give to your partner, ie yoga etc. The focus of counselling sessions is usually on the needs of the person seeking counselling, rather than on making suggestions about help for the person whose behaviour leads them to seek help.
Drinking too much is often a coping mechanism for people who are depressed. I'm with vampire in believing we are responsibly for ourselves and can in truth, only make changes in the way we respond to the behaviour of loved ones. Attempts to change others who don't see the need, or aren't yet in a place where they want to make changes, are unlikely to succeed.
Would your partner be prepared to move out and seek help so that your son has a calm home for this key period in his life. Whatever you decide to do, please put yourself and your son at the heart of any decisions you make. Look after yourself.