Another great episode!
The structure looked more to be a part of a door frame rather than an outer hull piece. In the "You will know the truth" pieces, you see Adama looking at these cracks in a door frame in what looks like his quarters. The old ship's taken a beating over the years.
It was pretty cool seeing the actual FTL drives. (I assume that's what they were) They certainly looked like something that was "spun up" and ready to use.
As for Zarek being responsible for the planned assassination of Rosalyn, I always thought that Ellen had a role in that. Telling someone where the assassin was when she was told at that bar on Cloud nine.
Again, anyone notice that Sharon seems very un-concerned that Caprica-six is getting very close to Hera? In just a few episodes before, she murdered a six because of her paranoia in this.