Ok, I'll give a stab at this,
1. It would be highly unusual to use the exact same 5V regulator for a analog sensor as your main 5V, if for nothing else then noise immunity.
2. Even if the 5V regulator dropped out, there should be voltage monitors which would have flagged this.
3. In addition, even if the voltage to the pedal sensor drooped/dropped wouldn't the redundant and opposing sensors either continue to work, or flag a fault as not matching?
4. Wouldn't you expect to see strange log data after an impact with a solid object, such as accelerator being stabbed at (as if it was the brake) but with 0 speed because the car has no velocity
5. And finally, if we are discussing a normal parking operation, why was the brake not pressed prior to any of this happening, as would be expected during a parking operation, rather only 5 seconds after impact. If one's foot were covering the brake, if there was an impact, that impact would tend to press ones foot down onto the brake in a sudden stabbing motion.
This seems like quite a lot of work. Since you are willing to put so much effort into this, I'm shocked that you haven't taken WK up on his offer to pull the low level logs from your car. I'd even bet that you could talk him into giving you a drive unit circuit board which you could check the power regulation on.
Peter