My girlfriends multi millionaire real estate mogul stepdad is on some weird shit help me

Right so basically I have been seeing my girlfriend for 7 months, all has gone well and we really get on, though recently she has stated to open up about her stepdad and this guy is mad weird. Just to prefix this aswell my girlfriend is very objectively conventionally attractive. To start with, when I went to her house ( fucking mansion by the way ) none of the bathrooms had locks but the holes for fitting were there, and she is always complaining about him walking in on her. (I think the dirty cunt did it on purpose so he can walk in on her) he can clearly afford locks I’ve never been to a house without bathroom locks before this and I’ve seen some gritty yards haha. Next red flag was when I tried to slap her bum walking up the stairs and she dodges it, exclaiming that her dad does it all the time so she’s used to it, I pry more and she tells me he’s been smacking her arse since 13 (this don is 53 bruv) and she constantly asks him to stop but he continues regardless. Also mentions to me that he physically punched her and slaps her for talking back and still does to this day ( she is legally an adult at 18 in uk ). Now onto the really unsettling shit. The other day I glance over at her phone and see a message ending in “you little cumslut” I grab her phone thinking she’s cheating on me only to see it’s her stepdad and see that he seems to address her by these vile sexual derogatory terms and similar all the time even for basic communication. Is this abuse ? Anyway moving on. The other weekend I went to stay at the house and toward the end of my stay I started to notice the place was crawling with cameras I’m talking multiple in each room all recording audio and video in HD 247 ( very discreet little things) then the day her parents got back and I had left, my girlfriend tells me at dinner her stepdad asked her “how was all that freaky sex you’ve been having with ***** ? (my name) this made me bug the fuck out because he was right we had been trying a couple new things as per say with the house to ourselves but how could he know that, I am worried the worst could have happened and they were cameras in the master bedroom on some Epstein level shit. Or audio captured us talking about it in the kitchen but that would mean he had basically listened to out every word. Anyway the final and most fucked up this this guy has done ( I could be wrong in fairness but I’m building a rico case on this prick) when she returned from college the other day she had left her MacBook at home with the stepdad ( my makes her call him dad for some reason ) she opens it up and starts doing work, she hovered over the search history and saw ( I’m gonna quote this word for word incase someone can give me info on what this is) “AI Nude Fit Create” on her laptop. To me this means he’s using her laptop because it has her photos on it to face swap her onto some kind of adult content. Or he’s trying to generate CP this is what made me put it on Reddit as it was becoming too much to no tell anyone. I have voiced my concerns to her a lot but she seems in denial and always want to dodge to subject. The other day she showed me a video from the ring doorbell of him slapping her and I feel I need to take action, the way I see it my options are : Street justice, I beat him to a pulp or set my dogs on him and give him a stern word( I fear legal action as he’s seriously rich as in Mayfair townhouse rich) Go to the police, I am reluctant to do this as they are so useless these days. Or leave her and carry on with my life and find someone who isn’t getting abused. (This sounds fucked up but put yourself in my shoes there is a 52 year old man grabbing my girlfriends arse on the daily and she won’t do anything about it) before you tell the mum to divorce him she is a trophy wife and makes no money nor seems to give a flying fuck about her daughter being abused as she gets to live the high life out the abusers pocket. Thanks for any advice and I apologise for vulgar language I’m quite passionate about this.