Thank you again.
Your jQuery test seems to be functioning and returning properly. I just now got a chance to disable all plugins other than yours and the custom post type CPTUI plugin. And I also removed all my .css and .js calls from functions.php in my custom theme based on BlankSlate or one of the other minimal empty wordpress theme packages. Your API & jQuery tests return the same thing no matter what plugins or scripts I do or do not have active.
I’m at a point where I can clone my theme into a new wordpress install/db and start fresh with your plugin. Let me know if there is anything I can look for before resorting to that, or in the process of rebuilding.
Thanks a million!