Datefilter - Limit dates to just dates from filtered custom field

We’re using the events calendar and then setting up a custom template with Bricks filters on a completely custom bricks query.

We’ve setup the date filter to use the Event Calendar’s custom field “_EventStartDate”. This works and you can filter the events by when they start. However it’s a festival with a limited date span and we’d like to be able to limit the date choices to the “_EventStartDate” options for the query not any available date.

How do I do that?

Site Here:

Current Settings

I’ve tried toggling the “min/max” option but that for some reason limits me to dates in January not March when all the events are happening.

Am I doing it wrong?

Thanks in advance.
Brendyn