Am I Wrong for this?

Currently I (18F)with my sisters (16F, 10F) and parents (38F, 40M) they're going through a messy separation due to incompatibility and a 2 year affair my father had with another woman. To preface their relationship has been unhealthy and unhappy for years now. Past few months my dad has been the primary breadwinner because she was expecting and on house arrest.

Just recently she got off and has been making money through door dash. I say all this to say that ever since they've been separated she's been telling me and my sisters that this summer she's making it about her and taking back her "freedom" and she advises us to find ways out the house so that she can't keep the baby with our dad. Which likely won't work imo because he has work back to back and he's no longer in the house with us he's either at my grandmother's house to stay (his mom) or the woman's house I'm not sure which but. For weeks now since I'm not in school and I work I've been watching the baby when she's out and my sisters are at school. And though I know what he did was wrong and he shouldn't have cheated on her and I do empathize with that

I can't help but feel like she's.... going about everything the wrong way and part of it has to do with her poor decisions she's made. Back when they had a terrible fallout a year ago she cried to me her daughter and told me as I'll never forget that she would never have anymore kids by my dad again. And yet we have a new sister here with zero help from him while he's with his gf giving her money and reaps the benefits.

My mother tries over and over again to reconcile and contact my father, she curses him out over the phone, blows up his phones either with calls or texts. She goes to the woman's house, constantly tries with him depsite him not caring about her in the slightest and choosing someone else over his family. He shows her time after time. It's embarrassing I feel embarrassed for her. He hangs up on her face. He told the woman he loved her and they been talking for 2 years. 2 years. My mother didn't even know what the word misogyny meant.....I treat their relationship as a cautionary tale of what not to do. And someone I never want to be. Its obvious how much she cares how much shes attached to him and how much he doesnt. Because she still gives him her time and energy. It's pathetic.

We're trying to plan trips and everything but we have no babysitter and I honestly believe this is the fault of them both. If your relationship is rocky and ur financially not in a safeboat to have more kids why have more? I'm parentified now all the time since she's constantly angry irritated and outwardly frustrated with the baby. And I feel resentful honestly because it feels like the weight and responsibility for her is on me her sister. I'm not her parent.

They both seem to constantly be finding ways to not be a parent to a life they chose to create and that isn't fair.

Advice?