I don't believe that any humans currently alive in the Fleet are any of the final five.
Remember basic Cylon history. They were created roughly 50 years ago as sentient laborers, that rebelled fairly quickly, and fought with the Colonies for about 10 years, leaving Colonial space 40 years ago, still entirely metallic. The two infiltrators we know of in human society, Caprica-Six and Boomer, first appeared two years before the holocaust (presumably Boomer was able to get into the military with hacked background information), so we have no evidence the humanoid models even existed before then, and they clearly didn't exist, or anything like them, 40 years back. Nobody who was alive during the first Cylon war could be one of the five.
From RDM's commentaries, the 12 humanoid models are what happened when the Cylons tried to look at humans and copy them. Each model is supposed to be what they see as a basic archetype of humanity. Since the 7 (now 6) operational models of Cylon humanoids don't know about the other 5, presumably they were deactivated before the other 7 were operational (or were operational at the same time and had those memories purged by whoever acts above them, like the Cylon intelligence that created the humanoid models in the first place). I think that the "final five" were Cylons who were too altruistic or benevolent for the Cylon mentality, models which would have never approved of genocide or a war of revenge and were Boxed for it. With the Thirteenth Tribe's tendency towards prophecy, they could have built the Temple of Five as a monument to those who gave their life to try and prevent a war against their descendants.
Some cut lines from the Kobol arc were going to establish that Kobol was a paradise until one of the Lords of Kobol became jealous and wanted to be elevated above all other gods, causing strife and civil war and the eventual exodus. I always figured that this was a 13th Lord, who went off and later took the Cylons as his own children, thus showing how they are related (like the whole Temple of Five and Athena-Boomer's comments in Home, Part II imply) but how the Cylon god says he is the only true god.
Who did D'anna see that surprised her? Who knows, it doesn't have to be anybody that the audience would also recognize, just somebody she would.
