A test I use for "which" is to try removing it from the sentence entirely. If the sentence still works without it, then you were using it wrong.
From the examples above:
the gist you mention, is the main topic of the video
But I also really enjoyed The Ballad of Mr. Steak, a stylistic precursor to...
(the Tesla sentence is just poorly written and needs to be rewritten. Maybe: "The point I was trying to make is that Tesla isn't prevented from driving by transportation authorities...")