Hi Z.
I think it's awesome that you're trying so hard to support your friend when they're going through something so awful, even when distance is making it extra difficult, and we'll do our best to help you work out some ways to do that. To start, can you tell me what country your friend is in? And to make sure I have a clear picture of the situation, are they the same age as you?
If you haven't already done so, do you think you could encourage your friend to report what happened? If there's already a restraining order or other legal order their dad is breaking, telling the people who put that order in place may be the quickest way to get enough protections in place to keep him further away.
I also want to give you this article:
https://www.scarleteen.com/article/abus ... xperienced. It sounds like you're really trying to do right by your friend, and that article has tips that can help you when you're doing that.