I'm estranged from my father who is dying and I couldn't care less
Why don't you care about your father dying?
He treated me like shit and he always made me unhappy at home
You don't think if he dies before you say goodbye you'll feel guilty? Once he's gone, that's it.
I have no regrets.
Instead of trying to muster up some empathy, maybe you should visit him and tell him how you feel.