Have you thought about doing an outdoor enclosure (preferably somewhere the smell wouldn't be too bothersome around the house, because obviously he'll do it out there)?
The leash thing is a good suggestion too.
I have a female cat that's a sprayer and the only thing that slows it down is giving her outdoor time. She doesn't do it constantly but she will do it on things that are new in the house and periodically in random places. She is fixed, it doesn't matter, I think it's a habit of hers and she was probably doing it before we got her (we got her as a rescue and she was already fixed and an adult). Luckily female cats spray doesn't smell as bad as a males, but it can still be pretty bad sometimes.
With your furniture you may wanna try covering in plastic. You can cover the plastic with a cloth furniture cover to hide it and that can just be thrown in the wash. It would make things a lot easier.
I've tried to find cloth furniture covers that are waterproof, kind of like the covers that go on beds, but no luck
. You could try making one yourself with a waterproof liner if you're good with a sewing machine, but it would be expensive compared to the plastic and furniture cover suggestion. It would look nicer though.