Thoughts on the loose formation thing: perhaps by spreading the unit out further, you dampen the impact of the enemy's charge. Their charge imprint is the same each time, but you (by spreading out) are putting less men inside that imprint, and thus more survive. At the same time, the enemy infantry must cover some ground to get to most of your remaining soldiers, which may mean the greater reach of the halberds gives you the first attack most of the time in the general melee. If your unit was tightly packed, it's more likely enemy infantry would already be close enough to yours after the charge to just start swinging away.