How sad.
Jmitw, google the "purrfect cat fence" and see if you can build him an enclosure so he can go out. I put one up for my cats and they've been a lot happier now that they can safely be outdoor cats when they want. That particular fence was not cheap -- $1000 (a friend paid for most of it, bless him) -- but if you study the design you might be able to do something on your own. Even if it's just a 10x10 enclosure it would probably help your kitty.
Right now cats are better than dogs because cats don't eat cat litter, get a wad of it plastered to the roof of their mouth, and drool all over the place until their owner finally gets their mouth washed out enough with a turkey baster to see that they're not choking, they've just got "cat litter paste" plastered to their hard palate.
Yes, that's how I spent 20 minutes about a half hour ago, swilling the new dog's mouth out with a turkey baster thinking I was washing a wad of it out of her throat before I realized she was grimacing trying to get it off the roof of her mouth with her tongue.
(On the other hand, dogs are better than cats because if I had to do that to a cat it would have bitten and scratched me until I needed to go to the emergency room. Molly let me pry her mouth open and shove paper towels and the baster in there and my hand at the end without any protest, growling, or offering to bite or even push me away. She knew I was trying to help her.)
Time to build a bigger bridge.