Well, even on commercial variants the usage of the cab/util switch is vastly different. On some of ours they have to stay on at all times, otherwise there wouldn't be any lighting available in the cabin. Somewhat weird setup to be honest.
To be honest, there is nothing in our documentation about the door heaters, which doesn't mean they're not there of course. Sadly i do not have access to our maintenance documentation.
Unfortunately there is very little technical content in Boeing FCOMs today. They have been deliberately dumbed down.