I have just caught up with this thread and I am so sorry to see how bad you feel and how your poor little one is deteriorating because of this horrible disease.
My boy Rebel has it too. He was diagnosed a couple of years ago and only became symptomatic several months ago, but the progress of the disease and its effects on him are awful.
Rebel is the opposite of your dog. He was booked in for eye ulcer surgery and a heart x-ray this morning, so of course I bathed and groomed him last night. He is now a retired show dog because of his poor health, so very used to being bathed and groomed and has always been one who cannot stand still for more than 2 minutes at a time but so vain that I have always had to show him his reflection in a mirror when he is done, so that he can admire himself. Last night there was none of this. He stood still as a statue and his eyes looked as though the lights were on but nobody was home. He didn't want to see himself in the mirror, just no interest in what was being done to him, he just wanted to stand there and wait until it was over. I too cried.
When I took him in to the vet this morning half of me wondered whether he would come through the anaesthetic or not. Something inside me said it might be better for him if he did not. When I got the 'phone call to collect him and to have a chat with the vet I changed my mind completely. When the nurse brought him into the surgery I was so relieved that he was ok.
Rebel does have problems and he may be going on to Gabarpentin fairly soon, but when I took him for a walk on the way home he was a slowed down but very happy little dog, sniffing everything he could find and meeting an adoring public in the local shopping centre. His tail wagged like crazy when the staff in the local greengrocery insisted that I should bring him into the shop, where he chatted up and gave kisses to both the girls. Life is good again for this little dog.
What I am saying is that like me you should not give up hope. Okay, this disease is very nasty and it is upsetting to see our dogs deteriorate like this, but if they show us they are happy and their quality of life is generally good, then shouldn't we just count our blessings and be glad that they are still with us.