1. From what I remember, that attack does damage based on the height of the user. So it can deal very large damage if Gisele is tall.
2. Blackjack or any of the casino games will not take up an action. Waiting in a time block will skip one and you will be left with 3.
3. You need to have Isabelle and Melanie both in the game. Both need to have over 500 height and Isabelle needs at least 10 wins.