I have tried multiple times to get Scrivener to crash on my system by using the process you described here.
Enter full screen mode
Write for a few minutes
Pause to read, do research on second screen, or go AFK for 5+ minutes
Click on screen to type again and resume writing
I tried that several times and never experienced any crashes, I even tried using another application over top of Scrivener on the same screen, then going back to Scrivener after a break from writing. I am starting to wonder if you are not experiencing the same bug as had been reported by Cenneidi here: Full Screen Error [BUG LOGGED]
Might not be the same, but I figured it could not hurt to point you toward that one just to double check.
The problems seem to arise from writing in full screen, exiting full screen to select another file, and reentering full screen. Not to say you don’t have a new bug that’s not showing up here, just that I am unable to replicate a crash without exiting full screen no matter how long I work on another screen or leave the computer between writing.
Sandra