I grew up with both parents as alcoholics. It makes you grow up way too fast. I'm sorry you're put in this position.
It's not your fault.
You can't save him, from his drinking or the consequences of it.
You can't protect him from himself and his choices.
I doubt your mother will be mad at you; you can't be expected to make adult decisions as a child. It would be wrong for anyone to hold you to that standard.
I wish I'd went to Alanon, or Alateen growing up. Perhaps you can?