With Junkion Nancy's station ability, if I focus and then scrap a card, is that +2 defence?
[Source: Aequitas]
No. Focus includes the act of scrapping, so Nancy only provides +1 defence to the stationed character.
Yes, but only as long as you decide to scrap the card that
Aerial Recon reveals.
If my character stationed on Junkion Nancy has Focus 3, do I get +3 defence?
[Source: Aequitas]
No. Focus stacks into a single event, so on defending, a character with Focus 3 would use Focus only once per each defence.