Not sure if you can get much from the video, but here it is running:
Last time it was ridden was 11/25/17. I clutched in and it just randomly died on me. I was able to jump start it and that's when the detonation started. I had to ride it about 10 miles home doing WOT in 3rd and 4th gear.
Starts up no problem, timing doesn't sound off. The coil/wires/plugs have all been replaced within the last 2-3 years.
Actually, the more I think about it, If one spark plug wasn't firing, the air and gas would go on into the muffler to be ignited sometimes by the other jug.
I think the first step here is to determine if one header gets hot first when you start it up.
You may just have a bad plug or some other dumb cheap thing.
When I have friends over and fire up my Firebolt, then they rev it at idle and foul my front spark plug, that's exactly what my bike sounds like.
The suggestion to check the temp of your header pipe is spot on. I carry plugs and the tools to change the front one with me wherever I go, you never know when someone is going to blip your throttle when the bike is cold...