My question is should I put my money in that can?
My answer is simple. No. He didn't earn it.
You can say that attitude is not Christian, and my answer is twofold: (1) Who cares? (2) Sez who? You can assert anything you want to about being "Christian" by quoting the right things. I could quote 'Eye for an eye" or 'Reap what you have sown" to justify complete indifference to this guy's condition.
But I know you're not indifferent, you have some empathy for his condition, but you have enough reason to dislike him that you're not motivated to contribute. That's OK and well justified as far as I'm concerned.
He didn't earn it. Not from you. Some people get sick and die, some live - them's the breaks, life can be really tough. Victim, aggressor, I don't care....he still made your life miserable. You aren't doing anything to hurt him, but you have NO reason to help him.
I worked with a gent who made my life miserable for three years, but who got melanoma and died. His brain basically fell apart. I didn't even go to the funeral, although I did sign the card that went around - because it was for his wife, not him. I've never felt bad about not attending the funeral; his death was a relief to me and I told my wife that. She understood and agreed, and she's one of the kindest, most thoughtful people I've ever met.