How have your proved that the one with footprints is fake, or are you not including that one in your list of fakes? To my knowledge that one has not been proven fake.
Not at its present size and resolution. It would be like trying to authenticate the tiny, compressed COLB image on Fight The Smears if that was the only copy ever shown.
When someone sends me an image similar to the size of the Factcheck/TampaBay/Daily Kos COLB, or Factcheck Photo #2, then I would have something to analyze.