I am not saying that the firing order is wrongh just that if it were it would prevent it from starting, at best it would miss all over the place.
As you have eliminated the coil as the bad boy, It could well be the phase sensor, which is why I asked if anything had been disturbed, just make sure it is plugged in, and make sure it is the correct way, the UPPERMOST wire from the sensor in the dizzy itself goes to +.
If it is the old sort with brown insulation that cracks when you touch it it needs replacing, the insulation falls apart, but newer ones have blue red wires with far better insulation.
As you say the phase sensor sends a signal concerning phase which if not present will cause it not to fire.
You are defo doing the correct things, so jsut a few more checks should see it ok.
The polarity of the phase sensor is important.
tabetha