AIBU for wanting to block and cut contact with my father [55M]? [16F]

[oksenva]

Sorry for any mistakes, English is not my native language.
My parents divorced 5 years ago. My dad left us for his mistress, stating he was starting a "new family" and it's never too late for a fresh start. He left me and my mom.
Since then, my mom has been emotionally dumping on me daily, constantly criticizing my dad and his new family. My older sister took a neutral stance but constantly criticizes our mom. I am trapped in the middle under constant pressure. I don't even know what my own stance is anymore. I was just a kid when they divorced. My mom dramatized everything, telling me every year that because of my dad, I was losing the best years of my life.
I used to see my dad on Sundays. We’d go to cafes, eat, and leave. I tried to talk to him, but he acted like I was the only one who cared about maintaining a relationship. Then we drifted apart. He lost his job and started paying less than what was set in their agreement. Eventually, it became less than what my mom makes now. My mom (56F) had to start working after being a stay-at-home mom for 20 years.
All of this triggered severe emotional burnout and mental health struggles for me. I lost most of my friends and basically couldn't study for two years. I had to crawl out of this dark place on my own. My dad refuses to take any responsibility for the impact on my well-being.
He used to give me allowance, but now every time we go to a cafe, it ends up in a huge fight with my mom because he complains about spending an extra $25 (2k RUB) on me, saying he has a "real family" to feed. He texts me "good morning" every single day, but there is zero actual communication.
I am exhausted. This one-sided relationship is consuming me alive. Am I being unreasonable for wanting to just block him and cut him out completely right now? Will I regret it in adulthood?

I'd be tempted to go low contact rather than no contact. People in their 50's don't always get it right - there is no rule book. Sounds like a tough time all round. Just respond when you want to, even if that's days later. Meanwhile I would try to focus on people your own age and have a bit of fun.

Does he add anything positive to your life? Support? Encouragement? Interest in your life? Do you feel loved? Or is it all exhausting and negative

If he's just a drain with nothing positive, I'd go NC. I went NC with my f when I was 16 and he was in his 70s. It was a relief, a load off my shoulders.

Id agree with the first poster, low contact might be the best for now. Stop meeting up with him if he isn't capable of guilting you about money when he does. Keeping him at arms length, whilst not making a declaration about cutting him off completely, would hopefully avoid more drama. Mute his messages and reply when you feel like it. You don't exist to make him feel better about his choices, and it seems like that's the role he's expecting you to play.