Kitten w/Broken "back end"

I posted about a calico girl with leg/joint issues in another thread a few days ago.

The same day I picked her up, I got a separate call about a tabby kitten dumped in a busy parking lot.

I went and picked him up as well, and all seemed fine except for a bad case of URI. Unfortunately I had to break my own rules for these two and quarantined the boy with the calico.

Little tabby boy went to the vet when I took the calico but I thought it was going to be a routine visit for some antibiotic to clear up his icky face. But the morning before his visit I noticed that he was getting into the litterbox, but not producing anything. Also, there was no movement or reaction from his tail.

So while he was at the vet for his URI, I had the vet check him. Not only is there no reaction in the tail, he seems his back end is injured, and he has no bladder control, or bowel control. His bladder was very full.

I have to express him several times a day. This is, because of the soreness of his back end, uncomfortable for him.

It has been 5 days since his initial vet visit. I took them both back in for a re-check and reassessment, and the vet is talking that if he has not shown improvement by now, his nerves are seriously damaged, and he is unadoptable, and likely to not heal.

What I'm reading online is that these types of injuries absolutely ARE recoverable, but it takes TIME (I'm reading 3-6 months) but amputation of the tail sometimes is recommended.

These two kitties (the tabby I am talking about, and the calico from the other thread) are humane society cats. They have taken on the responsibility of these kitties (financial) and I am their foster/daily care provider. So ultimately the decision for these guys is NOT mine. But I do have a considerable amount of input to give when it comes to decision making, and I want to give it more time for both of them.

I am not hardened, but I do understand that sometimes euth'ing is absolutely necessary and the best decision for the animal in question. But I don't think that is the answer just yet for these two. Am I off base here? I think a few days is just not enough time to make life/death decisions. And I'm not necessarily looking for medical advice, but more personal opinions, or experiences with this type of spinal/tail injury and rate of recovery?

Aside from his bladder/tail, he for the most part is a typical 6-7 week old kitten. He runs, he plays, he purrs, he smacks anything that moves, he DEMANDS attention, he is an amazing little turd. Nobody can convince me he is "suffering". I'm sure his injury is painful, but it is temporary. I'm sure he hates being expressed (he has told me this several times lol) but it also may be temporary..... The quality of life for this little guy is very high, despite his current condition.

All I know is, he was found in a busy parking lot. Nobody knew there was anything wrong with him, aside from the fact that he had not peed in the 10 hours or so that the people that found him had him. We noticed his tail did not work., and so it began. The vet feels he was dropped/hit/kicked/something that injured the back end. This must have happened immediately before he was found, because this injury causes him to poop on his own tail, and he was clean when he was found. (If this were an old, ongoing issue, he would have had poo on his tail from previous attempts to poop). So it would seem it is an injury, not a disease or genetics.

I think a second opinion is going to be the next step. I don't make those decisions, but I have given my opinion on this vet's outlook, and am hoping I can get someone in agreement with me to get them to see someone else.