Limit number of event registrations per month
Action to halt registration

Use "Page redirect", with a value for "URL" that could be either one of these:


some special node that you want to display to inform the user that the maximum number of events was reached.
the same URL that the user uses to add the event, combined with "Show a message on the site" whereas the message content provides appropriate information to the user that the maximum number of events was reached.


If that doesn't help/work, then you may want to try a variation of my answer to the question about How to restrict access to a node via node/12 and allow access via a path like content/sometitle? (that question was about "Node is 'going' to be viewed, while yours is about something like "entity is 'going' to be created").

Reset registration counter

Similar to the "Registration Count" field that you added, add another field like "Count start date". And each time a user tries to create a new event, just use that "Count start date" to compare it with the "current date": if then the time span between those 2 dates is longer then that "certain interval", then reset the "Registration Count" to zero.