In spot mode, the meter doesn't change. I haven't swept a flashlight across it, but I have swet the camera from looking out a bright window to a dark wall, and the meter stayed constant.

It is possible the secondary mirror isn't in the exact spot, but it is hanging down very close to vertical. I can see it by looking directly at the primary mirror. You can see it's pattern back through the mirror - which upon reflection sounds like it may not be hanging far enough back, because it should be reflecting that light down, not straight back at me...

You mentioned zippo fluid on the hinges. I don't have lighter fluid around, but would kerosene work as well? I'm guessing I'm just looking for a powerful solvent?