David's change
Had a few more thoughts.
Although from your comments and logically speaking, David's Change occurred between the party and when he was called over to Ballicec's, personally I've felt from the start that he was already Changed when we met him at the party. He was emotionless at Ballicec's but wouldn't we all be if called out in the middle of the night? Plus it seems he was not the best of friends with Jack who called him. I believe my suspicions stem from David's pushy and non listening way he treated the frantic woman at the party whom we all identify with. Yes his emotions at the party were much more vibrant but just figured it went along with the job.
Also totally agree that with so many to choose from, Matthew's last photo on the back of the movie cover was totally unnecessary. As in the original movie ending, we all want 'hope' that somebody gets away to warn others for a stop to be made.