The BCM "Body Control Module" controls all functions not related to the engine and transmission. Everything you mention points to a flaked out BCM. I just don't understand how a Multimeter with a 9v battery could cause enough amperage that it would take out the BCM.

Have you checked all of the simple items first like grounds, battery cables and trying another battery in it? I know when the battery in my 2004 GT1 went to a dead short all sorts of weird things would happen at the cluster.