How can I delete the notable event history? Nothing in there I care about. We had a few were testing and now they are in the history looking misleading.
You can use ES' Notable Event Suppression to get them out of Incident Review. Suppressions don't delete the events per se, but it will drop them out of your view. See the docs here: http://docs.splunk.com/Documentation/ES/5.1.0/Admin/Customizenotables#Create_a_suppression_from_Nota...
When you create the suppression, you will want to set a date such that it suppresses all of the notables before the given date (probably today in your case).