If you CAN open Dramatica Story Expert, go to Gist>Gist Manager, click on one of the large gist collections and press the Close Collection button. Do that for as many as you can to get it down to a reasonable number (20K or less gists).
If you cannot open Dramatica Story Expert, go to the Finder, select Go>Go to Folder and go to ~/Library/Preferences/Dramatica Story Expert 5 Prefs
Delete the Dramatica Story Expert 5 Prefs file.
Try to open Dramatica. If it STILL doesn't open, you'll want to move or rename your large gist files so they are different and won't be recognized.