Do you know of another FB in the area that you can compare with? Also have a nother set of eyes look at it.
Your grounded at the trunk as well? Might have to review the electrical systematics to better understand what's going on.

We need to isolate where the power is coming from (failed circuit).
If the car is on, headlights are on then turn off ignition car & lights stay on. At this point try this:

Unplug each headlight starting from LH to RH side to see if engine quits.

If the car quits you probably found the circuit problem.

Also, how are you front signal lights doing. They are buggers to keep grounded. Ground them with a wire clipped to the frame to be sure they are grounded.