I played around a bit with the widget you already provide, arlo, and I must say that it already suits my needs from a details- and formatting-perspective.
Might it be easier for you to allow a widget selecting events based on a Bandhelper-user (i.e. login) before creating a new JSON-feed on the long run?
I could imagine the connected database-request to check for the username instead of the project-number (which I assume is the current way it works).
If this would be an option indeed and you need somebody for testing, I will gladly volunteer
