How can I fix this situation?

[Guppax]

**I KNOW THERE IS A LOT TO READ BUT PLEASE DO NOT PASS THIS BY, IT'S VERY IMPORTANT**

My girlfriend of 7 months has problems with her parents at home. Her father is mentally unstable, a power freak, and keeps his children EXTREMELY sheltered. I asked 'Jane' out at a party on July 6th, 2013, at a party. (Her mother told her dad that she was going to a friends house so she could go to the party). We kept our relationship hidden from her father for awhile so we could figure out a good way to tell him, because as I said before, he keeps his children very sheltered. So, we talked over Facebook, and eventually, her paranoid father read her inbox and found out. Needless to say, he wasn't happy, but he let us go on for a little longer. Her birthday came around on the 27th of August, at a mall, and I was invited to attend. We took a picture when we got there, and she later posted it on Facebook (she was still allowed occasional access). Apparently, neither she nor her mother told him I was invited, so he assumed I showed up uninvited, and both her and her mother were too scared to tell him I was invited. Because of this incident, he beat her(i did not find this out until recently), and made her break up with me. About 2 weeks later, she decided that she would take the risk of staying with me. We've been found out three times since then, once by her mother, who agreed not to tell her father so long as she breaks up with me (she didnt), another time by her father who gave her the beating of her life apparently, and again, just today. I don't know any details about today yet, other than the fact that he is making her switch schools, wear uniforms, and he has taken virtually everything out of her room.

Sorry about the word wall, but I just want to include any details I can. So this brings me to my problem; I want her out of that house, before he snaps. The obvious solution is bringing her out when she's 18, which, if we can find no other solution, will be done. If she wants to run away from her home, I am also willing to do that, but for obvious reasons, I would rather find a better solution.

I have researched emancipation, but it says that she must be able to prove that she can be self-sufficient without her parents, but BECAUSE of her parents, she can't do that.

He DOES beat her on occasion, but as far as I know she has no markings to prove it.

My mother is totally willing to take her in, and that's actually our plan after she leaves her home.

Is there any way I can get her out of that house as soon as possible? I will answer any questions that I can, and you may contact me on skype at camo131 or you can email me at guppax@gmail.com if you want to talk to me individually. Any help will be appreciated.
@RC with his fists. She says he does it in ways that don't leave marks, I really don't understand but she definitely isn't lying. She has a little brother as well that I failed to mention, I don't want to leave him there either but I don't know what to do about him. To him, I and my parents are complete strangers.
@Susan Thanks for your thought out response. I have never had the opportunity to meet her father because he has never given me the chance.

To answer your questions;

Too young/old: That's not it. I'm 17, she's 16, and we're a few months apart.

Plans for future: Yes, he has her entire future planned out to HIS (not her) liking. He expects her to be married, but only to a man of his choosing.

Religion: I am not of his faith, but this isn't the problem as he doesn't know of my religion; however, he is homophobic and I am openly pro-gay. I understand and respect the religion of both my girlfriend and her father, but I am not a part of it.

Old-fashioned: Somewhat, it's more-so that he's narrow-minded rather than he's old fashioned.

Seeing people: He doesn't want her dating anyone, but that was because of her dating me behind his back.

About me: He clearly doesn't like me, but he doesn't know me, I am not sure of what he may like or disli
Unfortunately, it cut off my answers. Thanks for your advice Susan.