I am sorry you are going through all of this. I hope posting helps. It helps me to post and write in my journal.
I really commend you - It sounds to me like you are doing good for yourself - taking care of you - that is so smart. I am amazed at all the smart and strong things you said in your post while living with your situation. You can't control your brother's disease and you can't control your mom's refusal to get help for herself.
I don't want to say the wrong thing - but is there any way to help your dad? It sounds like he is stuck living in the situation and can't make a choice like you to take care of himself. I don't know if it would be a slippery slope to try to help him - but could you get him out of the daily living situation? I apologize if this isn't helpful.
Also just want to say again you are a smart, strong person. Hugs.