Have you checked the battery voltage is good? Anything over 12.5Volts is good, anything over 13.5 volts is not good.
When you have the bike in neutral and you turn the key to on, does th neutral light light up?
Checked all your fuses?
I have no ideas what inline ignition testers are, but are they reducing spark voltage too much?
Rather than replace it straight away, you'll know if the kill switch is causing the issues when you unplug it and short it out on the loom and the try and start it. If it starts, you've got an open circuit.