It is such a pity that your brother is so deep in denial about your mother's behavior that he is using you as a scape goat. You never caused your mother to have a substance abuse problem, nor are you at all responsible for her abusive behavior. She used you to vent her frustrations, that's all. When a parent hits a child, they are out of control and lack the communications skills to talk thing out without resorting to violence.
Your father did the right thing by protecting you against her abuse. I imagine she got on his last nerve long ago, but stayed to protect you kids.
Your brother has convinced himself that you are the problem, not your mother. He probably just cannot bare the truth and therefore, he cannot or will not see it or acknowledge the reality of the situation. Perhaps, like your mother did, he is using you as his scape goat. He has all of these negative feelings and rather than seeing it all for the truth of the matter, that your mother caused all of this upheaval, he is putting the blame on you. You see, IF you kept quiet and just took the beatings, mommy would still be home....that is his train of thought, as dysfunctional as it is.
Please, please find a way to forgive your brother for his inability to currently see and understand what actually happened. The cause and effect of your mother's behavior has nothing to do with you other than the abuse she placed on you is a symptom of her problems, not the blame of them. You are not powerful enough to cause a grown woman to be an alcoholic and make her abuse you. You do realize that, right?
I understand you love your brother and unless and until he has a true reality check, I am afraid he will continue to blame you for your mother's problems. But, the great thing is that often when people grow up a bit, they mature and see things differently. He may have a revelation one day. There is still hope that the light bulb will go off in his head when he finally realizes your mother's behavior was all about HER and HER frustrations, HER alcoholism, HER inability to cope with life, HER inability to effectively parent without abuse. She picked on you and she bullied you, but somehow, she had the control not to do the same to your brother (it seems). Maybe she did hit him and he thought he deserved it. Who knows what really is going on in his head.
But, time heals. Time will change his perspective on what has happened, it will. So, give him time and give him space and do not discuss your mother with him, should he bring it up, unless it is in a way that he acknowledges her problems. In the mean while, have light contact with him at first by acknowledging holidays and special occasions. He needs time to heal and once he understands the reality of what happened, he will come around. He will. Be patient.