I’m having the same problem and that was my first assumption as well. Bad coil. Also just as an aside I felt like I was learning from Tom Hanks, at times you sound a bit like him. Great tutorial though man.
Nice job and nice explanation. I am going through a no spark situation with a Toro 521 that the guy told me was the keyway in the flywheel. I put the snowblower together and I was right and the parts guy was wrong