That is wonderful. You are a guardian angel to that cat. I have a feral that I care for and don't know her health status, but I sometimes fear she is felv + or fiv +. She seems pretty healthy lately, but she had a few days about 6 months ago when she seemed really sick, and I was worried.
I'm so glad to hear your feral is doing well. That is amazing what you have done for him. I'm sure whatever time he has, and who knows how long, will be the best time of his life, now that he is safe with you.