I said this last week in response to another poster, but I think it's worth saying again. It's OK to choose, as I did, not to witness the self-destruction of the man you used to know. You have not chosen to refuse to be at his side as his life slips away; you have chosen to save yourself. That's a healthy choice; not a selfish one.
I agree with TC; the man you knew died a while ago. All that remains is an empty shell. Heartbreaking for you and for him. Just heartbreaking.