Gotta get this sorted out!

You majorly changed your opening post, start over time...
NGK plug heat range is colder as the number increases , higher the number the colder the heat range, the lower the number the hotter the range.
If you have spark arcing, fix that first.
Post a pic from your phone, look on the message box and it will have an add photos button above the more options button, post some spark plug pics. 600cfm is tiny for that motor.