My dad stopped praying and now curses Allah in anger

Assalamu alaikum, I’m writing this from a throwaway account. My father has always struggled with anger. He never laid a hand on me, my sisters, or my mom, nor did he ever shout at us, but he did get physically rough and verbally harsh with my brothers when they were younger, which wasn’t right. When he got angry, he’d curse the world or people around him, but it never crossed a certain line. Lately, though, things have gotten worse. We lost a family member some time back, and it hit everyone hard. He’s the one who shows it the most, but not by talking. He just gets angrier and cries more-something he never did in front of us before. We tried reaching out, offering comfort, suggesting things, spending time together. But he just snaps, or blames us for the loss, or says it’s our fault. So we backed off a bit. We still talk to him, but we keep it light because any attempt to help just ends with him hurting us. Then we noticed, a few months ago, he stopped praying. He was never super religious, but as long as I can remember, he always made sure to pray all five salawat. At first we thought we were imagining it, but no-he completely stopped. Maybe he goes on Friday, but we don’t know if he actually goes to the masjid or just somewhere else. We haven’t confronted him about it. I tried nudging him subtly-like saying I’m off to pray, wearing my prayer clothes around him, asking if he prayed-but it didn’t work. And the anger fits… about a year back, we heard him curse the One who cannot be cursed. It really scared us. We wondered if my mom had to remarry him or what to do. But we made excuses, thinking maybe he was so angry he didn’t know what he was saying, which can be forgiven in Islam, and he’s been under so much stress from the loss. But now he’s done it again. And insisting on a sin is inexcusable. I don’t know what to do. No one does. We’re making dua, but honestly, I feel hopeless sometimes. Any real advice would mean a lot. I’m not even sure what I’m asking for-divorce, confronting him, therapy, all of that feels impossible. I just don’t know. Alhamdulillah ala kulli hal.