You did indeed nail it.
My error was I was working so much in the ssh world for a few hours that it didn't occur to me until late that this was not an OS issue but an application issue. Setting up key pairs, no matter how many times I've done it, is so damn error prone that a repetitive motion disorder takes over.
I would add for others making this trip that a global change may benefit them. In my case the actual command was:
git config --global core.sshCommand "ssh -i /root/.ssh/id_omega255f.pem"
I had expected to see a /etc/git/ directory get created with a config file for the global change. Not so....apparently done somewhere else. Maybe some day (like later today) I'll need to find it. 8^o