It can freeze or crash even if I zoom in too quickly, with composites or Boolean operations I click then wait. It freezes for 6-8 minutes then completes the operation or crashes.
There should definitely not be any kind of delay as you're referring to (6-8 minutes). Feel free to save your workspace (*.wrk) and send it to me, I'll be able to review everything you're experiencing.
Suggestion #1: Typically most Gerber jobs are a meter or less (usually much less than that). Since your design length is extremely large for a Gerber job, I would recommend that you first set FAB 3000 to handle large database dimensions:
Suggestion #2: To speed up display times I would recommend the following:
Lastly, is there anything unusual about your computer setup (such as dual monitors, etc.) - maybe there's something obvious that is causing the delay. The more information I have the more I can assist.