Haven't looked at your file, but a few tricks I find are really useful are:
Use multiple Event Sheets - this will enable you to try many different variations of game mechanics by just 'Including' the relevant sheet.
It also enables you to pinpoint problems much quicker as you don't have to trawl through reams of Events.
I generally have separate Event sheets for things such as: Globals, Controls, Collisions, Scoring, Baddies, Loading, Saving, etc.
Readability is better.
Just my 2 cents