The takeover happened after you saw the cutscene of the Dragon fighting Damian's dragon and getting shot down, and before you woke up with Zandalor greeting you.
I disagree. At the end of that scene Damian stomps on the head of the Dragon, presumably delivering the final blow. If it was the case that Damian was there when Ygerna infiltrated the Slayer's mind, he would have not been so surprised at the end asking her how she managed to free herself, when he was trying to accomplish just that.
Unless you are saying that after Damian defeated Talana, Ygerna took the opportunity to jump in and pretend Talana didn't actually die during the dream, and had now taken residency in the Slayer's head. However, that is in no way implied by the cutscene which Damian refers to as a vivid dream. So I don't see how you are drawing that conclusion given the information. It seems just as much speculation as saying Ygerna was Talana from the get-go.
No, because Talana had a strong mind. Remember the warnings of Organa and Rhode - The dragon memory ritual left the slayer's mind weak and vulnerable, that's why s/he had to stay behind and not particpiate in the hunt for Talana in the first place.
Again, this is assuming Ygerna never actually overtook Talana's mind as a Dragon Knight, and only pretended to be Talana guiding you,(from the cutscene forward) which is not implied from the cutscene or any other surrounding events.
This explanation does not suffice for me, but maybe I am missing something.
