Hi Gary,
I don't think I can offer "advice", just my own experience and thoughts.
This last week I had to have my favorite society hen euthanized. She was crested with alternating white and chocolate feathers in her crest - quite stunning, and a little character in herself. She raised one fine nest of babies and I had hoped for babies looking like her eventually. Unfortunately she developed "twirling/stargazing".
I tried every treatment I was able to research, and thought at one point we had her on to recovery. She was able, right to the end, to keep herself fed and watered. And oddly enough, could even fly about her cage. But it was a massive struggle for her. She eventually couldn't tolerate ANY noises as they would startle her into a rolling, panicked bundle of feathers on the bottom of her cage.
I just had to finally make the decision that this really was no quality of life for HER. Trying to keep her going was beginning to be feel more and more selfish on my part. So I took her into my vet. Her discomfort and suffering were finished in a very quick moment. NO.. it was not easy, and it never is (I work at this same clinic and voluntarily oversee every euthanasia to try to help the families), but ultimately what was better for HER, was the best decision I could make.
And for now, I still have her babies who are a delight, and perhaps someday one of their chicks may bless me with another highlighted bad haircut
I"m so sorry you're having to go through this.. it's just never easy.