Sojourn, sorry I have no advice to offer you regarding Kobe, but I am sending along my prayers and best wishes that he recovers. Have you tried just offering him canned tuna or some other fish? It's not an ideal diet of course, but it may be enough to get his interest back into eating.
Don't beat yourself up worrying that you didn't do anything soon enough. Our animals are very adept at hiding their symptoms from us. Weakness is not a good thing in the wild so they hide it. That you are doing what you can for your beloved Kobe now is all that matters. Good luck to you Sojourn, and bless you for taking such good care of your boy.