Your situation with Soxx sounds so similar to mine with a neighborhood stray (definitely not a feral) that I took care of for several years - though I didn't have a camera to see what Mr. Casper was up to. He had a house, with a heated pad, on my covered deck (and then later in my screened-in porch when I moved), and he'd spend quite a bit of time there when it was cold. Otherwise, he'd disappear all day and come running for food. He was super affectionate, and occasionally left me gifts that I would have preferred not to receive. He liked to come in but only for a little while. He'd get antsy after a bit. I kept in overnight a couple of times so that he could be seen by a mobile vet. He yowled all night, and after the second time, was very hesitant about coming inside.
Anyway, personally, I'd be feeding him more. If I converted correctly, 90 g. is about 3 oz. For a kitty his size, and who is probably very active, I would think he needs twice that amount.
If he becomes an indoor kitty, he'll figure out the litterbox very quickly. One thing you could do at first is to sprinkle some soil from outside (and if you know where he pees, from that area would be perfect) over the top of the regular litter.
As Greenport ferals said, kitties used to the outdoors might not show a whole lot of interest in cat toys. One of my kitties had clearly been an outdoor kitty before I adopted her, and any time I got a toy mouse out, she looked at it with such disdain, as if to say "I've seen the *real* thing. What do you want me to do with *that*?" However, both she and Mr. Casper the stray would play with certain things - it was just a matter of finding what appealed to them.
It's amazing that he'll even let you give him tummy rubs! Bodes well for his potential future as an indoor kitty!
Last edited by marie73; 04-16-2019 at 12:11 PM.