Boy I chewed thru this thread. First thing I'd wrap your brain around Noomi and this is not a criticism but to change your thought process as a human.
He's not being disobedient. He's misbehaving. I'm not giving him a pass on his bad actions here, just trying to put it in perspective.
Think about it. Disobedient is when a command is given and not obeyed. This is misbehaving, but I bet dollars to donuts he doesn't see it that way.
You and your mother sound like awesome dog owners but you're just having an "issue" with this beastie. And from what I've read in this thread you've had him checked out so this is not an issue for the vet.
First thing I would do is deny the dog access to the couch. Stop the bad behavior. And if the JRT is now doing it, this boils down to marking.
In one of your posts you stated that this dog is like "supreme marker" beyond when you go on walks. My Bad Ass was that way. I swear to the good Lord above I've never had a dog who could squeeze out one last drop to mark where my neighbour's dog had whizzed.
I think that's where you have to start from. It's not about urinating on the couch, it's about marking the couch.
So temporarily deny him that access. Next up, nice and simple here, make the couch so unappealing that he never wants to mark it again.
You have to descent the couch. And make it not desirable to be marked.
Now you could put up a photo of Amy Winehouse....

keeeeeeeeeding but the easiest dog repellent ever is chili powder.
All natural and I've even been able to drive skunks and cats out of a garden with it.
Because this is a piece of furniture in your home, here's how to do it. Take masking tape and make a giant loop and tape it to the corner he prefers.
Then spread the chili powder on the masking tape. Now he's going to get the sneezies, but it won't hurt him. And you won't stain the couch.
Oh and a quick note before you start the chili powder, descent with hunters descenting products. There are so many on the market that are excellent I won't recommend one over the other.
But get that indoor fire hydrant aka your couch to not be a sniff/marker haven.
I understand other people posts and agree with the recommendations of more "working moments" but I think the marking is a completely different issue. And in my humble opinion I think that's the problem.
I bred some of the hardest working dogs on the planet. Catahoulas can do a swamp for hogs and can do a cattle roundup all on the same day. I love working dogs.
Here's a pic of the male I was talking about who had marking issues when he was a puppy. This is him as a young pup. This is my American Bad Ass. He was one fine beastie. I miss him so.