Thanks for the clarification, that makes sense and changes some of the dynamics.
Expanding on scenario B, if the unit charged was 3 or 4 rows deep, the first row is destroyed, the second row is pursued. Does the third row become the new supporting unit and therefore considered part of the combat?
So, if the second row is destroyed, the 3rd row can't strand and shoot as the attackers will pursue, not advance. But combat will stop at that point as 2 rounds had been fought.