1. No. (But I often wish that they did.
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2. No. The length of the weapon only helps with regards to repel, not to striking distance.
3. Not sure that I understand the question, but I often use heavy infantry in groups of 15 to 20 spread out in front of my magi and archers with hold & attack closest orders to help defend against flanking attacks. Heavy infantry to me is usually high protection and shields, but masses of chaff work just as well and take less resources to produce.