Oh, thank you so much for the update! Ritz is correct - he's getting overstimulated. Cats who have not spent a lot of time around people are like human loners - they don't know the social niceties and just aren't sure what is expected of them. So sometimes they miss our signals and give off mixed signals of their own. As you get to know one another better, you will get better at reading each others signals.
Is there a way you can add a cat door into the garage? It will give him an area of his own "inside" and perhaps get him used to the idea of being more of a housecat. It does sound like he remembers your kindness and has decided to take advantage of your hospitality again.
I would try to introduce Grimace (who is adorable BTW) and Fitz as slowly as possible. Cats really need time to adjust to changes, no matter how small they seem to us. Take it slowly and allow the cats to set the pace.
One more thing - if he stares at you, don't stare back. This is a challenge in the feral world, so a slow blink will let him know you're cool.
Is there a way you can add a cat door into the garage? It will give him an area of his own "inside" and perhaps get him used to the idea of being more of a housecat. It does sound like he remembers your kindness and has decided to take advantage of your hospitality again.
I would try to introduce Grimace (who is adorable BTW) and Fitz as slowly as possible. Cats really need time to adjust to changes, no matter how small they seem to us. Take it slowly and allow the cats to set the pace.
One more thing - if he stares at you, don't stare back. This is a challenge in the feral world, so a slow blink will let him know you're cool.