Such a great looking bike you got for sure!
OK, it dies with choke, that's normal and good.
Yes, black plug means rich and is loading up.
It does seem to idle well and bring itself back to idle after riding.
Do you have lower jets to try?
It really seems like a jet issue to me because it bogs on you when you try and take off and then comes to life as RPMs get higher. At first I thought you might need higher but now that I see, hear it and your plug was black, I think lower now.
Definitely fix the air leak too of course.