Question 1 - Back
There are only two hearts left in the deck to catch your flush so solidifying a non-foul hand on 9th street by pairing the 9's in the back row is ideal, especially when Villain 2 is on the verge of fouling.
Question 2 - Middle
It is still early to catch your back row flush, especially when no other players are carrying any spades in their hands. Moreover, pairing the Aces in the back row may not be enough to win any of your opponents' back rows since Villain 1 has a straight draw early and Villain 2 already has trips.