No power lights etc but ignition turns over?

Also the cranking symptom may be leading us down the wrong path. Analysis is "fine" but the thing is these problems can (and likely are) intermittent in nature and THINGS CHANGE right in the middle of the problem and in trying to find it.

Your main suspects (The Usual Suspects?? LOL) are battery cables/ connections, the main fuse link, the bulkhead connector, and the ammeter and it's connections.

I would start with Joe Biden's shotgun. You know, "fire two quick blasts up in the air?" What a dumbshit

ANYWAY pull the battery cables clean and inspect, and reinstall. Turn on the headlights and do some wiggle tests. Wiggle the battery cables. Wiggle around the bulkhead connector and harness. Wiggle the fuse link. Then go under the dash and wiggle the harness there, all the time looking for activity from the headlights.