Filter the venue name inside structured event data and always set it to the name of your theater. Place the code inside the functions.php of your theme. For use with the Rich Snippets for Theater plugin (http://theater.slimndap.com/downloads/rich-snippets-theater/).

wpt_structured_data_set_location_name.php

<?php
		
/**
 * Sets the venue to a fixed value inside structured event data.
 * 
 * @param	string		$name	The original venue value.
 * @param	WPT_Event	$event	The event.
 * @return 	string				The new venue value.
 */
function wpt_structured_data_set_location_name($name, $event) {
  return 'My Theater Name'; // Replace this with the name of your theater.
}
add_filter('wpt/structured_data/event/location/name', 'wpt_structured_data_set_location_name', 10, 2);