So it maybe closer to a 1/4 or 1/2 mile maybe?
I doubt it was less than ~850 feet given the distance from the closest side of the nearest rock formation to the turnout and I also doubt it was more than 1500 feet, assuming once again the nearest rock formation. If it was the farthest rock formation we're still less than 2000 feet so I would dispute a distance greater than 1/2 mile.
Going beyond that, we have a cave that RT mentioned that he returned to, to search for BT because after he got back to the RV and realized she was no where in sight he thought of other places to where she might have walked. I dismiss the cave theory because why would BT walk to a cave when she wanted to get to the RV. I do not know the location of the cave but I suspect walking to it would introduce much farther distances for BT to walk (unless the cave was located within the same rock formation) before she could arrive back to the RV. The cave search was just RT attempting to be thorough in his searching for BT before eventually contacting 911. Understandable.
I find the "abducted" when she "crossed that road" theory a possibility, albeit a remote possibility, and I also find that LE's "no evidence of Barbara was found" at the general location quite plausible, meaning, given the sparse attire and no backpack there wasn't much to leave behind. I suspect BT's cap could have fallen off during a struggle but such caps are usually stable if fitted correctly, perhaps a pony-tail/bunched hair was threaded through the adjustment band.
As for footprints, struggle disturbances, I don't expect such 'evidence' to be easily detected on dry, hard desert earth. The variance in makeup and disbursement (wind erosion) of surface material in such an environment makes detecting 'disturbances' somewhat difficult but, it should be easier to detect something that would be 'out-of'place' in such an environment, such as chips bags and candy wrappers.
Now, down to this: I find the "carrying a beer" aspect just a bit troubling in that, why would BT hang on to a beer or anything else not usable as a weapon if she were being abducted by force? It is possible the beer (container) could have landed on the floor of an opened-door vehicle during a struggle but for that to occur I expect BT would have had to have been very close to the vehicle
before the abduction action had begun; I can't imagine BT holding on to it while being dragged even a short distance to a vehicle. Heck, drop that beer, claw the abductor's face, etc.
The fact that RT emphasized the beer is the key element causing me concern. You state it as fact that the person had a beer in their hand, to ponder why it wasn't found at what you believe to be an abduction scene but not that it was part of the enticement for someone to abduct, which is how it sounded coming from RT during the interviews; his presentation of that supposed fact (carrying a beer) did not waiver. He never stated 'I didn't even find the beer she was carrying'.