I remember a student asking a teacher about a problem which was different in nature, but which was about the anxiety she felt about one of her parents, resulting from a lot of dysfunctional problems that they had when she was growing up.
He said that a lot of people have problems, and that includes parents. Before they became our parents, they already had problems (we don't usually think of our parents being like us, full of anxieties, terrible secrets, and things like that). Unfortunately, that is how the situation is. Buddha said that beings are tormented by all kinds of suffering, and parents make a lot of mistakes.
For the most part, everything people do, even really awful things, they do because they think it will bring them happiness. You mom sounds like a perfect candidate for this description. But their actions only bring more suffering. It sounds like your father is really suffering, or may be suffering more in the future. But when you think about it, your mom is really suffering! I am not trying to dismiss the importance of what you have told. Both my parents are gone, and my mother passed away very slowly and with a lot of mental breakdown. This is a big crisis for millions of people right now. At least your father will have people to (maybe) take care of him. It doesn't look as bright for your mom. Who wants to take care of an abusive, self-absorbed person like that?
There is a great quote by Shantideva, something like "Suffering comes from seeking happiness for oneself. Happiness comes from seeking happiness for others." If you think about it, this is really true. I feel bad for your father (my dad grew up on a farm) and also for you. But for your mom, maybe just pity. So for your own sanity it will help to have compassion for her as well as love for your father.
On the practical side, talk to an attorney. And discuss living wills and power of attorney. Also, if all of this is taking place in the United States, see if you can get your dad to give you all of his money and property now. No, I am not telling you this so you can cash in early. But unless your dad is broke, all of his savings will be drained to pay for his expensive needs that will bre coming up. It's better if you are keeping his money, for his needs, in your name.
Profile Picture: "The Foaming Monk"
The Chinese characters are Fo (buddha) and Ming (bright). The image is of a student of Buddhism, who, imagining himself to be a monk, and not understanding the true meaning of the words takes the sound of the words literally. Likewise, People on web forums sometime seem to be foaming at the mouth. Original painting by P.Volker /used by permission.