[Kobal2]

Yes, hits to the head happen. That's why there are separate protection ratings. Not sure what the probabilities are off hand.

Pretty sure trample trumps any weapon. You either trample puny yoo-mens, or use your weapons on equal sized foes (or larger).

Trample uses as much AP as simply moving into the square, so 2 for an adjacent one, 3 for a diagonal.

Each square of trampling counts as an attack, so encumbrance*opponenent squares moved into each turn. It adds up really fast, unless you're undead or a construct.

Not sure for the AoV, but I would wager a dome does block it, yes - AFAIK Returning (which is the spell the AoV autocasts when the wearer is damaged) is functionally not different from a Teleport aimed at the capital. I'd test it out in SP before relying on it succeeding.