As-Salamu Alaykum. Dealing with C-PTSD Related to My Father. Seeking Guidance.

Salaams, everyone. My father changed for the better over a decade ago after performing Hajj, Alhamdulillah. I have forgiven him, even without an apology, but my trauma automatically activates when I'm around him. He often invites me to go jogging, pray at the masjid, or do other things, but I usually politely decline with a reasonable excuse. I only join for Jumu'ah prayer or other activities where there will be a third person with us. Hearing his voice triggers my fight-or-flight response. I clench my jaw but try my best to have sabr, and Alhamdulillah, so far I manage by shutting down and just being a 'Yes, Dad' son. I know he provides for the family, but emotionally, I don't feel safe near him. I flinch at his movements or words when he's around. Because of a difficult childhood, I basically stay on the borderline between fulfilling the duty of respecting and caring for parents and that's it, because my survival mode switches on automatically. I'm the eldest son, 25 now. My younger brother didn't experience this as much because he came along later. Astaghfirullah, am I sinful in this situation? I am really trying my best.