How are you testing spark? It should jump a 7/16 air gap easily. Get the manual and start testing. The parts cannon gets expensive. I would guess your problem is in the switch box.
That is absolutely a diaphragm pump. Clearly shows them in the pic 5 and 2. If it gets its pulse from block pull that hose off and see if it's full of fuel. It should not be
You have a fuel issue. There should be no fuel in the bottom 2 cylinders for starting. The was a service bulletin for those motors. So the ones you gap should work fine. A spark plug should not cause hole shot issues.
