Sorry that I have not been keeping up with this thread as I should have, but I have only been online every now and thempn lately. I think there is probably some other issue that is going on with her. It might be aome organ failure, or she might be a failure to thrive chick. You are doing all you can do. Checking for a ruptured air sac was good to do. Usually when you see a chick with that, there is a large puffy area somewhere on the body that is air. When my 2 week old chick had that, it involved the whole right side. I needled it and deflated it a few rimes, and it helped.
It sounds like there is some improvement today. Mushy, watery feed can be tube fed several times a day. Apart from tube feeding, you can give some liquids done the chick’s right side of the throat that this article shows in the pictures:
https://unitedpeafowlassociation.org/articles/oral-medication-dosing-of-peafowl/
Here is a good video of tube feeding: