To address the HTW aspect of the OP, historically the Roman pilum was a one-use weapon, and the rules state that the HTW bonus can be used in the first round of combat only. I would argue that the HTW cannot be used a second time by the same unit, even if it has disengaged and charged again. IMHO, for the same unit to have the HTW bonus a second time against the same opponent appears rather 'gamey' and 'cheesy.'
"Experience is the teacher of all things."
~ Gaius Julius Caesar