Might not be a bad idea to clue in the doctors about the extent to which he is drinking. The only person you really have any power to control is yourself. At 29, you should be enjoying your life, not having to ride herd on an alcoholic. Do you go out with friends, have hobbies or interests you spend time on?
I still think Al-Anon is a good idea for you. And, as I said, your grandma if she is willing to give it a try. The fact that these folks raised you doesn't mean you are obligated to sacrifice yourself on the altar of alcoholic behavior. There are social service agencies that can step in to help with care. Could you afford to get your own place?