Cool and damp is a freakin death sentence. I'd keep 80% humidity, 85 degrees and not only would I soak him DAILY, I'd add Gerber strained carrots to the water. He may drink some, but there's pretty soft skin under his neck and nutrition may soak in there and in his cloaca. Not only would I soak daily and have higher temps, I'd remove the substrate and just have paper, avoiding and chance of rot on his plastron. He probably won't pull thru, however...we don't know that, so if you want to fight for him, stop the injections...start baby food soaks...also, this may sound hokie, but when I have a really sick baby like yours, I hold them and make sure they can and will stay awake...sometimes I think when they are really sick they just go to sleep and don't wake up, So I hold them and talk to them...anyway...I do that
