It seems to me that the main problem with the "Olver is Gaidal" theory is the age differential: Olver is nine years old, but Gaidal was spun out of Tel'aran'rhiod within the last few months. Despite the fact that time works differently in the World of Dreams, it seems highly unlikely that time could work that differently. But consider what Birgitte tells Elayne when ripped out untimely by Moghedien: "Gaidal is out there somewher, an infant, or EVEN A YOUNG BOY." (TFoH, 575, emphasis added). She thus implicitly recognizes that the sort of time differential that would have to happen if Olver were Gaidal CAN actually happen. Although the rest of the evidence is circumstantial, it seems that there is quite enough to lead one to believe that Olver most likely is Gaidal.