Dome light issue

72Ruster said
So from pin 3 (in socket) to ground, had about 9.7V. Car off. Between pin 2 and 3 about 10.6V. Voltage drop when grounded to body. Not a great ground but gave a consistent voltage.

You have a poor connection to ground. The door switches make the connection to ground when opened. Most likely a corroded connector or splice.