You may have zero scientific background, but your rule of thumb numbers are quite correct.

By simple volume, people have more to be concerned about from the plastic vapors left over from the packaging and shipping processes for the food they're buying from the grocery store then the risk of vinyl chloride contamination from the East Palestine spill.

I would expect that most food is processed in batches, so there could be a few batches that are very dangerous, but most would be completely unaffected (assuming the chemicals don't persist through whatever cleaning/batch changeover processes)