Please - check the OP's profile to read old posts to get caught up on the situation.
You are obviously very committed to your dog.
If you can prevent pressure sores and keep him clean while you see how he recovers from all of this, and if he is comfortable, and happy (relative to age - I think sometimes people expect puppy level bliss from an adult dog), I would give him the time to see if there is a bounce back. Eating is a big thing.
If he were unable to bounce back, then I would re-evaluate.
If he deteriorated, it would be time to make a decision.
That's just how I personally would evaluate it - with the very first question being, can I get my dog through this episode with really good nursing care. Because if that can't happen, then I am probably hurting my dog, passively.
And it's hard to take care of a geriatric dog going through a rough time. So I am not saying you should have a Hoyer lift and be able to do more than shifts of hospital workers could do - but sometimes the things are doable, and if that fits here, then great.
I like this from this website: Resources
You can get good ideas here!
Handicapped Pets - Helping Pets Live a Better, Healthy Life
and they have a forum, called a community, there as well.
Also really good info here:
Dodgerslist: canine back problems home page
Vitamin B shots - ask the vet if that's anything that might help. A lot of older people are on them, which is why I mention it.
Good thoughts to you, and your boy!