I feel bad. So he's missing his best friend and lying where he smells his scent, maybe, and is not simply wishing for attention. I'm sorry, I owe him an apology. Yes, I'd be keeping them apart, too, if they run around when playing. I don't see what choice you have right now. Poor Captain, if he feels like he lost his best buddy. I do remember a video of the other Tinker, once again playing with his housemate indoors, after he was healed. I don't think this link is going to take you straight to the post, I don't see a way to cite a certain post in the blog.
https://tinkerbeagle.blogspot.com/searc ... esults=100
This is the video
https://www.youtube.com/watch?v=Q5sLVDEuEOw&t=4s
Tinker (beagle) was paralyzed Feb '05 and the video is Dec '05 where they are playing together indoors under the watchful eye of their mom. The two dogs are the same size, though, and I think Tinker (beagle) was younger than your Tinker.
I don't know how it's going to be with Tinker and Captain, but I had a situation here with my first dog, Old Dog. He was unsteady on his feet (and eventually went down) when my neighbor got a new dog and not long afterward offered her to me because she was getting rid of her(!) I declined, then a few days later I saw Animal Control loading the dog into the wagon. I went out to the curb and took the dog and put her in the yard because she had no chance with the city pound back in the 90's. She was bigger than Old Dog and would romp around and knock Old Dog off his feet. With effort I was able to get the dog into another shelter. Then some time later a chow mix showed up and began more or less living in our front yard and guarding the house, as if she adopted it. This was not long after we bought the house, and there was still a stump of a large old tree that had been cut down, three feet wide, and she would stand on it and guard the yard. After a few weeks of seeing her and then putting out water, I let her into the back yard to see how she did with Old Dog. She accidentally knocked him into a sit,
immediately turned around with concern and nosed him in apology, and was careful with him after that, and she was welcome to stay.
It's a true story. The difference between Old Dog and Tinker might be that there was no chance Old Dog was going to participate in romping or start a romp, because by then he couldn't, so he was not going to get into an active play session where he might be hurt. I don't know if Tinker will want to do that eventually. It's all a judgment call but I know you'll figure out whether or how much to let them together when the time comes. Here is a link about back friendly activities after your dog has recovered from a disk injury.
https://dodgerslist.com/2020/06/15/back ... /%E2%80%8B