For example, with the emini S&P 500, some days it seems like the average move over 15 minutes is 2 points. Other days, it's 5 points. It would be nice to be able to figure this out so I can make accurate stop loss projections instead of relying on the Vix.

Obviously there is more volume at support/resistance levels but that doesn't explain the difference in between days like 5/12 and two days later.