Enjoyed your video. I just went thru all that learning myself.
(I never desoldered the ground from the top, just unscrewed the monitor clip and the earth wire ends in a ring that slips off the screw.)
I did take the four wires off the bottom to get the board out, but you need a large solder gun to melt a lot of solder as you found out with the green earth wire!
I actually fixed mine, something that a lot of searching rarely finds, unless it's a connector socket, chip seat, fuse, cap or processor microchip.
My dot was in the bottom center, whereas yours is in the middle right.
I did not have an oscilloscope, but did have other working Vec's to swap parts.
It detailed in this thread here:
I hijacked that thread because I went to post that exact topic and saw it was just created!
I'm in the USA, and the thread was started by a guy in the UK, I think, but hasn't reported anything recently.
Anyway, I am no expert, but you can message me here or email and I'll do my best to help.
I always discharge the tube first. It was my first time doing that as well. If you have just turned it off you will get a small spark, nothing like the snap I was expecting, but even a small spark can be deadly. The longer it has been unplugged the smaller the spark and after a couple of minutes there may be nothing at all like in your video. ( Which surprises me as I thought those charges would last longer, some tubes hold them for years!)