The fact that the engine is turning over tells me all the safety switches have been either defeated or overridden. Every rider I've had in the last 20 years wouldn't even turn over unless the clutch was disengaged, the PTO off and me sitting in the seat.
After seeing your video, it makes me think of an old Snapper LT16 that I have. It would run perfectly for about 45 minutes, then quit like I had shut if off with the key. It would crank over just like yours, but would never fire. I rebuilt the carb and fuel pump and replaced the ignition system....no change. The compression was around 145 on each cylinder, it was getting fuel and the spark looked strong enough. However, it still ran for about 45 minutes and then quit. Finally I got so frustrated with it that I parked it and bought another one.
Fast forward about 4 years to last winter. I decided to build an offset mower to pull behind the JD. I decided to use the deck off that LT16, and thought I'd give the engine one last try before I went and bought a new motor. I pulled it off the tractor, cobbled together enough wiring and a fuel system to make it run. Guess what, it ran perfectly. Something in the wiring on that old tractor frame was heating up and killing the motor. I never have figured it out, just glad the engine works.
My point.....disconnect all the wiring on the engine from your mower frame. All you'll need is some way to get power to the starter, and a wire to kill the spark when your ready to shut it down. Using a solenoid will make starting it less dramatic. I'm assuming everything mechanical has been triple checked. It's obvious you've got air and fuel, the only thing left is ignition. Something is killing your spark.
BTW: A blown fuse will not affect spark or fuel delivery on that engine.
