So you have 12 volts or so at pin 49? ANd this NEVER changes? But you measured the switch from pins 4 and 8 as:

No push - infinite
Push to Lock - 200 ohms
Pust to Unlock - 0 ohms

THAT is correct. So, when you press "Unlock" the voltage HAS to go to zero. If it does not, then, since the switch is good, either the connection from pin 49 to switch pin 8 is open or the wire from switch pin to ground is open.
THat is all it can be. In fact, I would like to know, if you press the button for Unlock and see full voltage at pin 8, if you can, probe pin 4. If it is full volts, that proves the ground wire is the issue. (Not sure how easy it is to get to.)

Remember, ground is 0 volts, when you press unlock, you connect pin 49 to ground and it MUST go to zero volts, if it does not, you are not really connecting it to ground.

Look for pin connections from switch to wire that LOOK like they are mating but aren't. Look for 12 volts on the ground wire when you press Unlock, there should NEVER be 12 volts on that wire cause it goes to ground.

The other pins from CLP/SSM are fine, that voltage changes when modules go to sleep. This is all about getting pin 49 to go to ground/zero volts on Unlock. THat is the 'Acid test". UNLOCK iS GROUND.