For now, until you get him to the vet, you might consider covering the couch with plastic sheeting, just for your own sanity, and because it'll make it less likely he'll get up there. I would try staying outside with him, walking for longer, and sort of seeing if you can get him to drain the tank! But peeing in his sleep is a reason to see the vet.

Do clean all the places he has peed with a cleaner like Nature's Miracle - which will remove the enzymes that we cannot smell but that tell him "good pee spot here!"