Not sure if this will help you but when I had an ill baby chick that wouldn't move, eat or poop (and did not have any sign of pasty butt) I wrapped her in a hand towel and used part of a qtip to feed her water saturated with savachick electrolytes (really, really concentrated) and sugar. I fed her a little bit every 30 minutes or so. In between feedings I warmed her up by blowing a hair dryer on the towel in which she was wrapped. At first she was too weak to complain or squirm. Over a few hours she felt a little stronger/more squirmy and I decided to get some much-needed sleep. When I went to free brooder 5+ hours later I had a little box with me.... Just in case

..... Thankfully, she made it. I think the liquid gave her just enough sustenance/comfort/whatever to fight off her affliction. I hope your little feathered one is able to recover. Whatever happens, please know that you are doing everything you can including reaching out to this community for help. I wish you the best.