1: The weight of items in your bags / pockets etc. and what you carry all add up. However I hope that what is in your backpack is offset in some fashion,
IE: 70% of the backpack weight goes through to you, so you can carry an extra 30% of wood in your arms.
2: - Quick looting will only be what you can see. A sword in the hand or scabbard, dagger. Anything else loose and not tied down. You will not be able to loot a belt or find hidden compartments in a quick loot. Quick Looting only while in-capped, cannot do inventory looting.
Inventory looting will be more indepth and only when coup de gra'd. This will involve looking in backpack and taking the belt and scabbard for example/
Full loot will be on permadeath, then everything/anything you possessed is fair game to those that find it.
Note: Coup De Gra is not perma-death, unless you are on the last tethers of your souls life.
3: Whip out that dagger and start butchering. If you have a cart then hope you have the strength to drag it onto the cart for bringing back to town for the butchers... I imagine levels will yeild different amounts. Low level you are likely to mess up skinning the bear and ruin a good chunk of the leather. Higher levels you skin it better etc.