Find a home for your cat and get him out of harm's way. You didn't even mention his name so I feel that for his safety he needs to be in a home where he can be loved and cherished and not abused.

Get some counseling as soon as possible. The abuse that you have directed towards your cat is dangerous rage for whatever reason. I don't want to play pop psychologist here but I feel you're on the brink of doing something much worse to your cat or to yourself.

As Catty1 said, saying goodbye is not only ok, it's essential. I believe in putting people first but it's imperative that you find this cat a home and then tend to the business of taking care of yourself.