Dena, is it possible to build a ramp for him to get him down the stairs?
And yes it is possible that they miss material. It's not tragic, just means they may have to go in again. Yeah it's tough, but people go through this kind of surgery too, sometimes twice.
That they did remove much of it means he should, generally, be in less pain over a wider range of motion. There may be only certain positions that cause him any pain but, otherwise, he'd be a normal healthy dog. I think it's too early to tell at this point.
Do NOT give up Dena, not for something like this and don't judge the results too early. Animals do not heal the same way people do and I've seen such a variety of responses to surgery; animals we thought were lost come back stronger than ever and animals that should do well, fade.
You're doing great, JB sounds like he's healing, and I have every hope that this thing can be beaten. If he needs another round of surgery, then he does, but worry about that bridge when you have to cross it.
Animals do not suffer memories from surgery. They do not hold it against you and if they survive it, they bounce back to their normal selves. I daresay this may be a world harder on you than on him.
How do I know this? I worked at a zoo and assisted with surgeries. I was a keeper of small primates but I assisted with all kinds of animal surgeries as I really wanted to be a vet. Sadly, I discovered I had a learning disability in math so I was unable to continue, but I loved that job and learned an enormous amount living with all sorts of animals every day. All the keepers covered for each other so we cross-learned specialties. Later, when Tristan became ill, I spent an enormous amount of time at the Animal Medical Center in Manhattan talking to every vet who would give me the time of day (and they did), learning everything I could about lymphoma and major surgeries on dogs. If I ever thought that Tristan would be worse for having his surgeries, I would never have done them. But he didn't and the great majority of dogs don't. It's rather amazing. That hospital works miracles. I've never seen such kindness and dedication in any hospital including human hospitals. It's staffed by angels posing as the most brilliant vets in the country and the kindest, most generous support staff anywhere. If you ever give-up hope, though it's a continent away, come here and get a consult. They do miraculous work.