Abusive Dad, No Physical Proof, Want My Siblings And Step Mom Out.

I want to start this off with saying im looking for advice or opinions on next steps I should take.

I am 20 years old and I have not had a consistent relationship with my father ever. He was always physically, emotionally and verbally abusive to me as a child. He disappeared when I was around 14 and I hadn't talked to him from the age of 14 till 2 years ago because my brother was born and he felt I should know. After I was informed that, we continued back to our no contact and I didn't meet my brother until he was a year old. After my first visit to meet my brother and new step mom I seen my dad had not changed his ways at all but seemed to be attempting. After that visit we went back to not speaking but I kept in contact with my step mom. She's a lovely lady and still continues to talk to me almost daily when she's allowed. I'll get to that. After some time my dad tells me I'm having another brother, same thing happened as the first time no contact till baby was born then didn't meet him until this October he is 7 months. After I went up to that visit it all was clear that he had not in fact tried at all. During the few hours I was there he had picked my 2 year old brother up by his wrists and dragged him into his room and double locked his door from the outside. I sat there for a half hour listening to my toddler brother beg his dad to let him out and hug him. He left my 7 month old brother in a parking lot in his stroller alone. He called my girlfriend disgusting and raised a hand to her as if he was going to hit her because she didn't clear the bong before handing it to him (we smoked some weed after the boys went to bed on the back deck) My step mom brought me and my girlfriend across the street to the bong shop and he messaged her calling her names and saying she's doing anything to avoid him He told me and my girlfriend to babysit while we were there while he went to work Screaming at the boys to "shut the fuck up" My 2 year old brother has a friend that came over to play and the little boy went up to my dad and said "_____ has a Spiderman toy!?! That's cool I have deadpool" and my dad screamed at this poor boy "(name) JUST SHUT UP THEY ARE ____'S TOYS NOT YOURS UR NOT HAVING EM" Called the friend gross cuz he peed his pants (he's 3 and still wears pull ups and my dad put him in underwear) Made me sit down and learn to roll a joint cuz "it's embarrassing I'm his kid and don't know how to roll a joint" My 7 month old brother was crying cuz my step mum put him down for a nap and went to the store to grab some supper, and my dad laughed looked at me and said "ur brother seems pissed eh" and went outside for a smoke leaving the baby to cry until his mom came home to comfort him. Me comforting the 7 month old didn't work as it was his first time meeting me so I was of no help:/ And I walked in on him doing Cocain in the washroom.

That was all in about 8 hours. After I left I received screenshot from my step mum of their chats of my dad calling her names, insulting her, lying to her ect. On a daily basis Saying how she's not allowed to speak to me unless he is watching. She is not allowed to see her dad unless it is away from the house and he knows about it. She is not allowed to have social medias that he cannot log into. He made her go pick up stolen goods (she didnt know they were stolen till she was stopped by cops) which caused her to get put on house arrest for a bit. She went out with her friend for a few hours to get out of the house cuz they had been screaming and fighting and he messaged her saying he bundled up the kids in negative temps and took them and locked her out of the house so she couldn't get back in for her curfew. He didn't do that but when she got home he was screaming again. Eveerytime she tries to leave he threatens suicide or to take the boys (she has 2 boys not In her care that are now older because her ex husband and previous issues in her past) So she doesn't leave. Currently on a curfew by law and her po checks with my dad to see if she's at the house.

I barely hear from her now as she's not allowed to talk to me and I can't see my baby brothers. I've meet the oldest 2 times and he's almost 3 and I've met the newborn once and he's almost a year old. I want my brothers and I want my step mom safe because I know what my dad is capable of. He never leaves marks so she doesn't have that "proof" She has no one where she lives as she lives an hour and a half, 2 hours away from me. And can't get to my city without it being a thing with my dad. I need help
I want my brothers and her out and I want him away. Forever. Gone. How do I proceed with this and what do I do.