rtrudeau,
It sounds like your dad has some serious anger problems. Have you talked to your mom about this? Or your therapist? My father has an anger problem as well so you are not alone. He often just explodes for no reason and is very emotionally abusive to us.
I am afraid that there is no easy answer to this. Without a wakeup call or some professional help he is unlikely to change his ways. The most important thing is your safety and the safety of your sisters and mother. If you feel unsafe there are resources available to you.

Stay strong,
Jessica

<font color=blue>The worst is over now and we can breathe again
I wanna hold you high, you steal my pain away
There’s so much left to learn, and no one left to fight
I wanna hold you high and steal your pain</font color=blue>
~Seether and Amy Lee