Managed to delete Event_Calendar_Status and cannot reinstate
I have not checked the module, but here are few things I can suggest take a database backup before you take any step.Uninstalling calendar module should be not helpful, as it seems settings to be changed in event_calendar module.

How you deleted the status term,did you make any direct changes to database?can you revert back those changes? You can setup event_calendar module on fresh drupal installation to track what changes can be done to make it work.

Not sure, but keep uninstalling and reinstalling event_calendar module as last option.

I guess event_calendar provides UI for mailing notifications settings, as the project page says


  This module also gives an Admin UI to change status (approval/denied)
  of events and a mailing system.