I'm so sorry you're going through all of this . . . I can at least somewhat relate - my family has never been normal, and the parent roles for me are the same - Mom is always the scary one, and Dad's the comforter and protector. Difference is, my parents were never together, so there was no split for me to go through, and I lived with Mom and visited Dad. Mom did alot of stuff that has left me really angry and bitter toward her, so I can certainly relate to that feeling.
I don't have much advice, except to agree - try family counciling, even if it is only you and your dad going. If nothing else, the two of you can learn how to cope with the turmoil - particularly your dad, because he seems to be the most vulerable one. And also, you can learn to accept the fact that you can only control so much of the situation.
"A face without freckles is like a night without stars"