I suspect the transmission is locked up between two gears thus the starter can not crank the engine. I suggest you unlock the transmission first then try the starter . If it has been physically unable to turn due to the tranny lock and multiple tries at starting it's possible it has been damaged. If it does not engage and turn after freeing the tranny then remove it and have it checked. That being said it does not explain no power to the other electrical components. As mentioned above the wire to the ammeter needs to be checked and also the ammeter itself. Also when checking for continuity the test meter should be grounded to the engine not the battery . 

@dennis-christianson  The small wire that feeds the dash from the starting switch post has nothing to do with the cranking of the engine.

@steve-d If John is attempting to crank the engine with the clutch pedal down, it would eliminate the problem you describe, for purposes of starting the engine.

Mike

I was talking about the gauges and lights, guess I didn’t make that clear.