Which Jackson is that? I've heard that they have jumbo frets. If yours has them, how does the action feel?
Regarding sounding great in a mix, but not so great solo, I have not experienced that with a bass, but it reminds of how many accounts I've heard engineers liking how the venerable P-Bass sounds in a mix. Interestingly though John McVie played an Alembic on Rumours songs and on "Rhiannon" from the Fleetwood Mac album he used a Precision on "I'm So Afraid" . Perhaps because it was harder-edged than the other songs.
I've never heard them h
Sounds like he's downtuned. Is that a little clam in when he goes to the second chord of the solo?
But he makes it sound like he meant to do that.