Go back to the battery box and recheck the fuse holders. Break a fuse in half so you can drag test the female connections one at a time. Better yet take pliers and gently squeeze the the terminals to tighten them up. Often the truck side of the fuse holder will loosen from heat and lose contact. Both side of the fuse will test good but the blade of the fuse isn't making contact. Have also seen the wire connection where it is crimped into the battery terminal get loose. Also if you have "cube" fuses make sure they are OK and the connections are tight. They are about 1 inch square and will be right on the battery post. There will also be some 2 and 3 wire connectors. I will post some pics. Take them apart and look. If they are bad it will show. I usually cut them out and hardware. They cause a lot of intermittent problems. Take the nuts off the mega fuse or fuses and make sure all the terminals are secure on the wires hooking in. The starter hot post is used as a junction. The terminals on the wires there can be broken, they look OK but aren't. The load test with the head light is a good test. Thought I had better pics in file.
