TestComplete 11.0 - Memory Issue

Defined All object references in one script file as Global Variables.
There are 3000+ Variables.

What is the purpose of doing this? It probably isn't causing the memory issue you're facing, but it seems redundant and unnecessary if you know how to use NameMapping properly.

As for the memory issue, can't say I have the exact same problem as you, but I used to notice TestComplete would use more and more RAM if I was using it over the course of a day or two without restarting it. I eventually came to realize that the SQL DB connections I was opening weren't always being closed because the test script would sometimes be interrupted and the code to close the connection wouldn't be executed. So if you are opening DB connections or files or anything else that could lead to a resource leak I'd suggest trying to make your code more robust to ensure any open resources are closed. I used the OnStopTest event to close any open connection I might have.