Hey there and welcome to the forums!
That’s a really nice design for filters — excellent work!
When you refer to the “main filter bar” are you referring to ur Filter Bar add-on? If so, you can absolutely use the additional fields you create in Events Calendar PRO (Events > Settings > Additional Fields) in the Filter Bar settings (Events > Settings > Filters).
Also is there a documented way to search on blur/release/keyup/click, etc?
No, I’m afraid there is not. While I don’t have any examples offhand, I’d imagine that can be accomplished with Javascript that targets the filter components and fires on any of this triggered actions.
Cheers!
Geoff