Cats don't differentiate between one piece of furniture and another when it comes to a no-go area. Jose only knows that you are unhappy when he goes on that couch, and he might get a squirt, so he only does it when you can't see him and will vacate the spot when he sees you coming or the squirt bottle coming out. When you're gone, he'll do what he wants to do. For that matter, the other cat is probably up there, too, and you just haven't caught him. Or maybe he's just staying off because he feels like humoring you.
OK, that last was a joke!!
Sorry, but the only way to deter a cat from going on furniture ALL the time is to make it unpleasant for them to be there ALL the time, even when your back is turned or you are gone.
Try searching the forum and the internet for posts and articles on cat deterrents, behavior modification, stuff like that.
BTW, putting him in a room while you are gone, as long as he has all he needs in there, plus the company of the other cat, would not be cruel at all.