My dad it's getting worse

Things are really getting worse here. My dad is in an affair with a 21 year old whom we found out is a friend of my oldest sister’s. They don’t know we know who it is yet. From what marriage counselors have said and my mothers own opinion, it seems my dad has a mental problem. And that makes me want to reach out and help him. But he’s scary. He’s this type of person who is very strict but also has a funny playful side. I haven’t seen that other side in a while. I can’t wrap my head around the mental thing because he was the most controlled, decisive person I knew. Now I don’t know him at all. He heard me singing a rock song and demanded to hear it. Then he told me to not listen to rock music anymore. But I love rock music. I’ve lived for it, and Black Veil Brides. And no one is going to stop me. Then, he seemed like the strict, dependable person I knew. But again after, he yelled at me for dripping water on the floor. He can be very scary. I have been thinking of moving to L.A. and being a rock singer. But with that dream and my dad, I just don’t know. He’s wanted the best for me and my sisters, but he used and still uses hard, unkind means to get the message across. It scares me. And My mom is in a lot of pain and crabby and irritable lately. I feel like I’m bothering her all the time.
We have to get him back, but at the same time we don’t want to. It just hurts. Please advise

First things first, keep doing the things you love, even if others don’t approve.

Mental health issues are difficult to understand. People experience symptoms differently, just know that despite his mental illness he still loves you. Same thing with your mother. She seems to be going through a tough time and might be stressed out. Doesn’t mean she should take it out on you, but also doesn’t mean she doesn’t love you. If you need to seek her help with problems, don’t be afraid to, I’m sure she will do her best to help you when she can.