When I turn on the headlights the engine shuts off, it will not start until I turn off the headlights

One evening, I noticed I no longer had instrument lights, but the van started and seemed to run as it always had. Later, while driving on freeway, I needed to turn on the headlights. I am not sure whether the problem happened immediately or a little while later, but the engine just shut off like the power had suddenly been shut off. Fortunately, my location allowed me to coast to the next exit ramp and the coast into an O'Reilly Auto Parts. Unfortunately, no one there could explain why that happened. I tried a few times to get it running again but then decided to wait until the next day to continue testing it.

The next day, I returned to the car with my friend, and he got it to start. It was harder than it usually is to start but he got it going and it seemed to run well, until we turned on the headlights, at which point, it shut off again. However, keeping the headlights off,
I was able to drive it home.

After a while, I could not start it even with the headlights off. In our initial tests, we found there was no fuel getting to the Throttle Body. I then determined that there was always power to one of the switch terminals of the fuel pump relay, but no power getting to the line side of its coil.

Of course, it can be difficult to track the power through the various harnesses, but I found one possibly pertinent fact. About half of the fuse box under the dashboard has no power going to it. The fuses for ECM B and the parking lights are among the fuses that are getting no power.

In one of the videos I watched, someone put a jumper cable between the powered ECM 1 fuse and the non-powered ECM B fuse, and his vehicle started right up. Of course, one would not want to keep it like that because I believe that energized all of the non-powered fuses grouped and the current would all be flowing through the ECM 1 fuse.

If this happens when I try this, I would suspect there is some kind of open circuit between the battery and that portion of the fuse box, but I have not found a wiring diagram showing all of the items the current would be flowing through on the way to the fuse box.

In the attached photo, the fuses with no power to them are the two 20-amp and one 10-amp fuses on the far left and the 5-amp fuse on the top. (Actually, for correct orientation, the image would be rotated 90° clockwise.)

Any thoughts?