3. Lip flaps don't really matter. In fact, it's kind of weird how anal U.S. dub companies get about them. They will put far more effort into lip-syncing a dub than the original production company does when making the show in the first place.
I certainly appreciate the effort, though. As cynical as it may sound, I think the reason they don't worry about lip-flaps in Japan is because they don't feel like bothering, not because it's not important. Otherwise you wouldn't have the occasional high budget film where the character's mouths are matched to the dialogue. It's probably because they're on a tight schedule. So to get the best possible performance in the least amount of time, they forsake matching lip flaps.
Plus, because English and Japanese are such different languages, taking lip flaps into account prevents them from using a word that's too long or short in the dub to actually fit the movement's of the character's mouth. Otherwise, you have character's mouths still moving without words coming out or people still talking with their mouths closed. I just did a little check of my own of the Japanese version, and stuff like this is really quite noticeable.