IF your kitty is truly feral that is a very sick cat. Usually they will disappear and hide when they are seriously sick. A semi feral is willing to be around people but skittish. They have semi trust in their humans.
Keep an eye on him. You may need to trap him and take him to a vet which is use to dealing with ferals and medical issues of outdoor cats. Lots of things can happen to outdoor cats. Eating unsafe things, being bit or injured. Or sometimes they have FeLv or FIV and experiencing symptoms of these diseases.
You are a wonderful person to take care of this kitty. I saw the house and all the good food. He is a lucky cat.