Okay after looking at the map, it's not exactly how I do one switch randomization. However, I think the problem is that you have it subtracting a bit in the triggers where you are adding the powers of 2.
You should subtract deaths of independent command center in the trigger where you randomize switch 2.
Also, I like to add deaths of the bit instead of subtract.
I would do it how heimdal describes it:
http://www.staredit.net/index.php?tutorial=61