Need guidance on dealing with my father’s behavior - JazakAllah khair for any advice

Assalamu alaikum. I’m 30, married to a wonderful wife, and we still live with my parents for various reasons. My wife is fine with it. To keep it short: my father was very strict growing up because he wanted us to succeed as immigrants. Over time that strictness caused lasting emotional harm. One of my younger brothers died from epilepsy last year - he’d been struggling for years and saw a psychologist for a couple of years. He blamed our father in part for the childhood trauma. I don’t think Dad is to blame for everything, but some of my brother’s pain was related to how he raised us. Allahu a’lam. My mother is ten years younger than him and has mostly kept quiet her whole life. She’s silently carried so much, doing things behind his back to keep the household functioning and to protect us. Lately she just snaps - she’ll get angry, not speak to him for days or weeks when he does something without consulting her or acts in a way she thinks is wrong. He acts like he’s always right and treats mental health lightly. Maybe he’s slowly coming to understand, but he needs to accept that others aren’t like him. As the eldest, I’ve had to shoulder a lot. I can’t say it made me stronger without cost - inside I still grieve and wish things had been different, and I wonder if my brother would still be here. I’ve had to confront him many times; I’ve raised my voice enough that he won’t try to talk down to me or my wife now, but I still worry for my mother. I know talking harshly to parents is wrong in Islam, but if someone prays and still won’t change harmful behavior, how do you reconcile that with being a good Muslim? I’m staying in the house mainly for my mother because she needs support. I’m struggling with what the right approach is. Please, if your only advice is “calmly talk to him,” know I’ve tried and it doesn’t sink in - it just goes over his head. I’d appreciate practical, compassionate suggestions on how to protect my mother’s wellbeing while maintaining family ties and staying within Islamic guidance. JazakAllah khair for any sincere advice.