I don't know what to do here. Parent problems.

It's no use to comment on your father (unless you want DRAMA) because there isn't enough information.

But have you thought about how this break-up will affect you? I don't want to go into details but I've grown up without a father and I can tell you that it will fuck you up in the worst of ways. It's nothing you will notice right away - nothing that you can immediately put your finger on, but a few years from now when you have the benefit of hindsight, you'll see how different - how much easier - life could have been with both parents.
I won't go more into that, partly because if I was in your situation, I would disregard this advice and treat your father like a scumbag that needs to be shoved out as soon as possible.

If you do feel very passionately about booting him out of your life, here's some food for thought. Giving up on anything is damned easy. Have you ever had a girlfriend? Just think about it - it takes so much to find that right person, to get the courage to talk to them, to find spare time to spend with them, it takes so much to make it work ... and a single sentence can destroy it all.
Giving up on kids, on relationships, on goals, on schoolwork, on most anything really, is just too easy. It's a measure of character if you can stay focused, strong and tough it out. Your dad probably isn't perfect and you shouldn't accept his faults - you ought to tolerate them until he fixes them. And work with him to fix them.

Man, it's just that-
It's bloody easy to give up on stuff and not consider the consequences. Getting a divorce will fuck all three of you up and the only thing you can think of now is "porn, omg".
I probably seem bitter now but really man. Don't rush this. Step back and think about stuff through and through.

Jam it back in, in the dark.