My gaming group recently started our second game of Shadowrun 4e, and I have a few rules questions, mostly regarding adept powers. As the resident rules lawyer, the GM is relying on me to tell him how to run the game

First, does the killing hands adept power turn damage done to a subdued opponent from stun to physical?
Do critical strike or elemental strike apply to subdual damage?
Does the +1 damage bonus from critical strike add damage to attacks using elemental strike?
Do hardliner gloves' +1 damage stack with critical strike? Elemental strike?
Do bone density or bone lacing augmentations' damage bonuses stack with any of the above bonuses?
Can an adept wearing a helmet use the cannibalize metamagic? The text doesn't suggest that any additional action is required beyond doing physical melee damage, but implies that the adept should be able to consume the flesh of his enemy.
Could a mage using a firearm in melee range gain the drain bonus for the sacrifice metamagic?
I read on other forum that a focus can have its force increased by paying the difference in material and karma costs for the new force of the focus, but I can't find that anywhere in the source books. Is this a house rule?
And now for a VERY conditional question: If an adept with the power bleed metamagic absorbed the essence drain power from an enemy, could he use it increase his essence to double his natural? Would this essence disappear when the power wore off?
Thanks in advance for any insight into these questions. Most of these are likely to come up in our game. My gaming den is lousy with powergamers.