The backpacks are 80-160.<br/>The chest would be 400ish.  I think STR15 to lift it (with issues), STR8 to push/drag it, STR20 to lift it over your head.  Though it is big enough that multiple people could work together (two STR10s to lift)<br/><br/>You could realize that they are up to something nefarious and drop shaken if you'd like.<br/><br/>If you were guarding the cart it would probably be central to everyone.  So it would probably form a 'wall' with Brin above or below it, and the other two somewhat offset to the left or right.  I will leave the exact details up to the group, since it would depend how the characters set up their camp.<br/><br/>A medium/heavy load somewhat counts as armour (lower max dex bonus, ac penalty, slower speed).  If you lift more than your heavy load you lose your dex bonus to AC and can only move 5feet a round.<br/><br/>"A medium or heavy load counts as medium or heavy armour for the purpose of abilities or skills that are restricted by armor."  So in theory they would negate the penalties, though a medium load is a -3 penalty and a heavy load is a -6 penalty.