Nice write up. One suggestion, although it's probably too late now, but since you got all the way to the blower resistor, you might want to drop the blower motor and clean the fan blades (There probably is a mouse nest in there as well since you found mouse debris in the cover). If I remember correctly, it's three more bolts and a little bit more swearing to drop the blower motor. Another way to clean the blower fan or at least the stuff in the fan cage, is by removing the top cowl (same one used to remove or replace the siren) since the vent on the passenger side has a direct view into the blower motor fan cage.