1) Does the Crippling Strike extraordinary ability of the Rogue stack with the Crippling Strike extraordinary ability of the Justiciar, if the Rogue/Justiciar is using a sap? I would think so since one arises from sneak attacking a target and the other arises from doing non-lethal damage to the target.
2) Is the sap able to be changed into adamantine, silver or cold iron? Common saps today are a metal piece (typically lead) wrapped in leather. In addition, are any of the magical enhancements (other than keen) unavailable to the sap, i.e. wounding, flaming or mighty cleaving? Would the flaming enhancement do non-lethal damage?