Just to make sure- the schematic shows an "Interior power kill switch", which is between the breaker we have identified, and the inside fuse panel. You have checked it, I assume?
To test with the meter, set it to 50 volts DC range, put the black lead to a good ground (or the negative on the battery, if it's close) and touch the other to the copper colored post- which will have power, because everything else works, and then test the silver post.
To be clear- if you test like Ken said, a *bad* breaker will read 13.x volts, and a good one would read 0. Instead you want to test relative to ground.
I'll add that for troubleshooting 12 volt power problems like this, a 12 volt test light is far better than a meter, and easier to use. Just clip the wire to a good ground, and probe away.
