excellent write-up....outstanding trouble-shooting....a tough one for sure. though you swapped them around i'd be tempted to replace the key switch relay(they're cheap and cross over to ford and chrysler a/c relays available auto parts stores) and also remove windscreen and carefully check the ignition switch plug and harness. i'd also spray something along the lines of kano kroil into the ignition switch key slot....work key around...try again. can you completely disable/remove that alarm system and see what you have?