By all intents and purposes, Axle appears to be just fine. The FS believes he either had just been really bruised or I cracked one of his ribs. He is playing with the other cats, eating on his own, drinking water. The only behavior I haven’t observed is the litterbox. I haven’t been home to monitor him and I don’t have an empty room or a place to put him that would show me he is using the pan.
I will talk to the vet tomorrow and see what she advises me to do. Hopefully, this was all just a bad scare and he is back to his fiesty normal self.