".....how they would all get out of the aircraft in the event that something went wrong?"
In a less than orderly fashion I would suspect. That said, if the aircraft is in that much peril, I would suspect that any exit that you could fit through would suffice.
That said, other than military aircraft (who would hopefully eject), I don't recall the test crew ever leaving the aircraft, in recent times at least. In fact, quite the opposite has occurred, with less than favorable results in one unfortunate case.