To my knowledge, Baltar never tested Tyrol using the Cylon Detector. However, I honestly don't think it works on Final Fives.
I have it on good authority that the writers actually consider "The Battlestar Pegasus Flashback DVD Movie" coming out in Fall 2007 to be "episodes 1 and 2" of the 22 episode Season 4. Not "episode 0" like the webisodes.
The first episode in January 2008 is "episode 3".
Agreed. It stands to reason there is only one of each model of this group, and it seems they are "more human" than the others. One would think this would apply to their physical makeup as well. They may well be undetectable, either as a result of their evolution or/and as a means to hide themselves from the other Seven models, given the gulf between the two groups of Cylons.