The problem I previously posted about turned out to be super-simple. I made a novice pointer mistake. In EPAppleScript (the second portion of code), "errorDict = &globalErrorDict;" needs to be changed to "(*errorDict) = globalErrorDict". Instead of changing the contents of the pointer, I just masked the pointer-argument by overwriting it with a local pointer. Thanks Jeff and Peter!

I could've sworn I tried that at the beginning, but obviously I didn't closely look at that part of the code again when trying to figure out the problem.

Moral of the story: mind your pointers.