One question comes to mind, has he ever sought professional help for this?
He can get through this, there are times when one must seek help if they want to move forward, and looking into seeing a therapist would benefit him greatly.
To hate can be just as natural as to love, but getting hung up in either's web can be dangerous.
If I were your dad I would look into seeing a mental health professional, life is too short to live miserably, and today it is unecessary, there are many options. . .choices that can be made.
I wish you luck with this all.

DE

In giving advice seek to help, not please your friend
SOLON