You know, this has been bothering me in all JT games, but is there any advantage in firing at a target with a whole stack selected, instead of firing with a single unit at a time? I've gone through the manuals, but can't really recall whether or not this changes the effectiveness of fire.
No change to the effectiveness. It does allow the stack to fire before any defensive fire but at the trade off of firing all units when one at a time may have led to firing at more than one target, such as if the target disrupts.