Yet another confirmation of the "make sure scratching surfaces are tall enough - they should be tall enough that your cat can stand on his hind legs, completely stretch his front legs up the post, and still have a little room above it. Horizontal scratchers (like the cardboard scratchers) can be shorter, but even so, if they aren't big enough, most cats won't use them. I have a double-wide inclined cardboard scratcher. (Yeah, it's not hard to make the same kind of thing... I just bought because it was easier.)
And, as others have said, try different types of scratching materials. Different cats have different preferences. Most people swear by sisal, but I've yet to have a cat that liked scratching the sisal. No, all mine have preferred the plain-old carpet covered - probably because those make the most mess once they start really getting shredded.
Speaking of messes - I haven't had to deal with the peeing issue (well, except for a cat that died a few years ago, but his were known health issues that made walking and standing difficult for him). But if it is an issue where the cat does not like to use a dirty box, you might consider one of the automated boxes. I had a LitterMaid years ago, and it was ok, and not much more expensive to use than a regular box (I just emptied and re-used the plastic containers where the box dumps the waste.)
Now we have a Cat Genie - it uses plastic pellets, a cleansing solution, and water to wash the pellets after each use. It's a mixed bag. We prefer it because the box is always clean for the cats, and we don't have to scoop. On the down side - the pellets get tracked more than regular litter does, and it's difficult to deal with that. And there are some known issues with the boxes - mainly with the water sensor - that means you sometimes have to fiddle with the thing frequently. And, of course, it's kind of expensive. Even with all of that, we've found it's the best solution for us.
Having a box that is always clean, though, might be an answer.... but if he just still likes "marking", even though he is fixed, there might not be much you can do except keep him confined when you aren't there to see him.
Two final suggestions for the scratching - citrus-scented Febreeze. Most cats hate the smell of citrus, so if you spray the couch with a citrus scent frequently, that may help. Also, it might only take a couple of weeks to "train" them out of using it... you might be able to use the Febreeze for a short time just to discourage them.
And the second suggestion - I've recommended these before (and I don't have any relationship to the company, we just found they worked well): Jumpo trainers (http://www.jumpotrainer.com) They are basically two hard plastic squares connected with a very short bungee. You set them (similar to a mouse trap, except they only make noise), and the slightest touch makes them go off. They are LOUD. If you can arrange these such that the cats will set them off any time they try to scratch, that might work. I've found them to be VERY effective. The ones we have are bright green, and we don't even have to set them anymore. If the cats even see that color of green, they won't go anywhere near it.