Chiming in here. I've worked with a former Joker writer, Terry McDonnell, who filled me in on this. Now to be clear, this won't answer all of our questions, but I can tell you this for sure...
The non-Mystery Category categories had FOURTEEN questions apiece. After each five-episode taping, the writers wrote questions to bring every category back up to 14. According to Terry, when he worked there, neither the show bible nor the contestant briefing even made mention of "In the event that we run out of questions," because the feeling was there was no way it was ever going to happen. Terry's departure from the company actually coincided with the arrival of the Mystery Category and before the introduction of Fast Forward, but I'm presuming the regular categories continued to have 14.