Thank you for reaching it. It's a really brave thing to do, and I'm so sorry to hear what you're going through. Domestic violence is really difficult to go through, and whilst I haven't been through it, I can imagine how hard it must be for you, especially because ultimately the abuser is your father.
It's understandable that you feel guilt from moving out, but from my perspective, I am glad you are safe. I think it's important to take care of yourself because you need to be well and safe in order to help your family. So that should be your priority. Go to counsellors to help with your guilt, speak up to people and groups you trust, share your experiences if you feel comfortable here on the forums etc. Exercise, meditate, go out with friends to take a break from the situation. Self-care is important.
In terms of your mum and sister, I think it might be worth weighing up the support he is providing with the abuse. For example, if the support is financial, is it worth the pain and danger of abuse? Domestic violence is very dangerous physically, but also mentally, because it can drive the person to depression and anxiety, which is an illness that I think, if left untreated, can be life-threatening.
Most likely, the support is not worth the pain, and your mum and sister would want to escape this. Can this support be sought from elsewhere? There are community and government services that might be able to help with this, and if you feel comfortable sharing the type of support required, we might have some ideas here on the forums.
I also encourage you to encourage your mum and sister to seek a mental health professional, especially your mum as she is dealing with depression/anxiety. I've heard that with many domestic violence cases as well it can be hard to put an end to it because of the familiarity and attachment to the abuser, who is often, as in your case, a family member or spouse. I cannot even begin to imagine the difficulty of loving someone and then they become an abuser. Therapy might help with this sort of thing if this is the case.
In terms of getting a longer restraining order and involving police, this is ultimately up to the victims, and as Hayfa said your mum will have to want this, though if you and your sister do I think you can also make an application (my legal info here is not 100% so pls check). But overall it might be worth having a family discussion with your mum and sister about what you want moving forward.