You definitely have found a rather interesting area full of cool stuff.
Your theory about the river not having a name can easily be argued the opposite way. Also, the person that made the map may not have known the name of it. And even if you solve the stone maps, unless the "treasure" also leads back to a person, there will never be a way to know the answer. So I wouldn't put too much emphasis on the river not being named.
As far as the map leading to gold. I've continuously read people say that the circle within a circle symbols refers to gold, but I've never seen that stated any where as fact. So I've also had my doubts as to what the map leads to. One theory I've had is that it leads to copper mines. In which case, the huge copper mine(s) right there to the east of the Superstitions may have been the places this map led to...18 places where copper ore was visible from the surface. Which would mean that the map is useless now. Who knows?
IMO, I think the biggest question is why the maps were made out of stone? With the writing and numerals on all of them, they definitely date from a time when paper was available. I don't know the actual weight of them, but they don't look light enough to merit carrying around in the desert to track down a specific place. It would seem more likely for them to be put on display somewhere... for example, in a "church" of some sort that believed Weaver's Needle was some sort of holy spot, and everyone could see the maps and know how to get there. Honestly, why make them out of stone bothers me quite a bit. Which obviously brings up the question everyone has asked themselves (that has looked into this) are they fakes? I obviously can't prove anything about them, but I do tend to believe that they are real. Mostly because that would be a lot of work to go through in order to drum up what? Money? Other than attracting treasure hunters to the Superstitions, they haven't made much money for anyone.
Just some food for thought.

BTW, caches of gold have been found all over Arizona around monuments and such, even one with Mayan numbering. If I were you, I'd put aside the Stone Maps and just hit that area you found with a nice metal detector.
PBFred