Before I comment on the images I want to tell you that I have a great deal of respect for the effort it took to obtain your photographs. It takes someone with a set of brass balls to go poking around the SWA alone. So, hats off to you for your effort! And again for presenting your discovery on the TN.
My first question to you would be why are the two horses, the suggested one highlighted in your photo and the one found on the stone so stylistically different? Didn't you insist that the artist sat in front of his subject and copied what was directly in front of him? Not to mention that this example is facing in the opposite direction. Did you obtain any close ups of what you believe are carvings? Are there tool marks or any signs to prove that this giant horse is something more than just natural cracks and shadows? What was the response when you showed JS Woods? Did he agree on the archeological importance of the site?
I think it is a good effort, but as I have said in the past. Stretching, distorting, or altering the images on the stones in any way to fit ones solution would (in my frail mind) invalidated the attempt -IMO.
We are looking for a perfect fit and because the horse does not exist in the field, complete, one could (and have) spend a life time searching for it only to find things that look similar.
This is pareidolla and in the Superstitions it sometimes can get the best of even the most discerning treasure hunters.
My feelings on the second image are about the same, but at least here you seem to understand what the symbol for "mountains" looks like.
Anyway, I think that you deserve credit for your effort.