Cool. Glad you got it sorted. I like to do the Master Bounce nulling thing in pretty much every project, just to make sure everything is rendered in the final mix with no missing parts, automation failures, dropped MIDI notes, etc. Plus it ensures that I have a final mix saved with the project. 
 
It helps to freeze synths and FX before doing that bounce to eliminate as much plugin randomness as possible from the null test. And if you have lots of sub buses with FX on them, you can bounce groups of tracks with bus FX to stems that route to the Master, solo those and then bounce the Master. For me this applies more to 3rd-party projects; my own stuff is not usually that complex.
 
When I'm happy with it, I'll export that track, knowing that I'm going to get exactly what I expect without having to triple-check my export settings. I also often do the final fade out on this track using a clip fade rather than messing with automation on the Master bus.