My dad is cheating on my mom and I feel miserable

Hello everyone. I posted a while back saying how I told my mom that my dad was cheating and you all were very sweet and supportive and I felt so much better. I just have been miserable for the past year because my mom keeps kicking him out and then forgiving him. They argue almost every night. My dad comes home late a lot and the girl he’s cheating with has the audacity to call my mom and text her and curse her off telling her things like p**** stinks and what not. My dad has bought that woman so much already and has taken her on vacations. We were going on a vacation to Florida a couple months ago and we used the wrong credit card and saw my dad and the girls name pop up. He was going to bring her to Florida and keep her in a different hotel while telling us that he wasn’t able to make it till later that week (this has happened for so many vacations we found out.) he says the reason he cheats is because my mom drinks and gambles and steals from him (which is true) my mom calls the cops a lot and yells and gets very violent and when she does this I feel very conflicted because my life feels like a disaster. My dad is a cheater and my mom gambles and drinks. I am sitting here typing this at the police station because my mom is drunk and getting a restraining order on my dad for coming home late. The police know me well already because they have been at my house so much. I just want them to divorce already but things keeps going in circles because my dad acts good for a couple of days and makes my mom think that everything is okay and she forgives him and then they go back to cheating again. I don’t even know why I’m posting this. I like to keep my feelings in and don’t really tell anyone about this. I’m 20 years old I want to move out of the house but I can’t because I have younger siblings at home and I can’t leave them. I only have one friend who I don’t like to burden with my problems I am single and have no one to comfort me and I just feel so alone. I was also thinking of horrible ways I could get revenge on the girl because she knows she’s with another woman’s man and she calls us and curses us off she doesnt want to leave my dad to be with his family because he has money and my dad doesn’t want to leave my mom because she doesn’t want to lose half of his money. I literally have followed my dad and caught him at the girls house and he says a bunch of nonsense excuses and even though I tell him not to come home he comes home anyways. But then my mom does things like gamble (I’m talking thousands of dollars a month), drinks (a bottle of grey goose a week), yells and throws things and she has been doing this for a long time even before my dad started cheating. I just feel lost and alone and I need to post this somewhere. Even if no one reads it.