1. Yes, you can
exile the copies, they are considered spells on the stack, just like
pack rat copies are considered creatures on the battlefield.
2. Exactly what you think it does. After lethal damage has been dealt to the blocker(s) the remaining damage will be dealt to the defending player. This includes the double damage (and part of the initial strike, if your guy has more power then the blockers toughness.
Does that make sense?