WELCOME ABOARD!
Sorry to hear about your recent loss. Good thing it's only a game. I'm also pretty sure that moving the crew has no effect at all. I'm not sure it made all that much difference in real life, given the tons of water moved around in the trim tanks.
As far as distance goes, I think you have to see the ship sink for it to be recorded as a kill; or at least be within striking distance so the crew tells you it happened.