My cat is a barn cat (kinda somewhere between a house cat and a feral cat, I found him outdoors as a young cat and despite being neutered still doesn't get along with other cats, but is also super sweet and cuddly to me and other humans he likes) and I still struggle to keep him indoors. I've only recently started keeping him indoors 24/7 (and I've had him for 2 years now), and there's even rats in the basement for him to catch and eat, and he still isn't happy with it. I'm worried for him because I'm about to move into a one bedroom apartment that's no more than 600 square ft, and right next to a busy road, so even with his leash I am not sure if I'll be able to take him outdoors.

If you've got any tips on how to keep a previously outdoor cat happy inside, I'm all for it. He doesn't like playing with cat toys, lasers, strings, moving toys, really nothing that isn't alive can keep his attention which makes it difficult.

Realistically I know he'd be happiest as a barn cat keeping critters away from food, but he also has separation anxiety and needs to check on me every few hours, so I don't know that he'd be any happier if I gave him away.