Final Update:
We are home...
Some other details. It ended up at one point a great deal more serious than I really went into before. He developed viral encephalitis, swelling of the brain, had what they termed the equivalent of a psychotic episode due to it affecting his brain functions for a time on Monday.
As they treated him Monday afternoon though, he progressively got a LOT better, and he was almost entirely himself by Monday night.
So, all ends well. A couple followups to go on Friday, and as long as it looks good, this is all behind us. Thanks to everyone for the thoughts.
I'm attaching a pic of him I took in his room when he found out he could go home and gave me the thumbs up sign.