work upon yourself, your life and as soon as you able to stand your own ground, setup rules to help out your mother, as per your post your father is not worth to continue a life with.
So first make your life and your brother’s life on a standing ground and then remove your father out of it and shock of it should be remain hidden to him till then. Do plan a separate living out of father’s home after standing your ground.
After that give him a reasonable time come to terms if he can, otherwise let him go of your 3 people’s lives.