Are you sure that's correct? That directly contradicts what I've read about airborne lead contamination in indoor shooting ranges. I'm certainly no authority on it, but everything else I've read on the subject indicates the vast majority is due to primer lead compounds, and extremely little from metallic lead.
Also, the base of the bullet does not normally vaporize from the heat and/or pressure of the powder charge burning. The exposure time just isn't enough to do it.
Yes, very sure. It's been documented in numerous studies and has been noted by owners of compensated guns. The Speer FAQ does a good job of explaining it quickly and you'll find a lot more data online...
It's also why "lead-free" ammo is always loaded with a jackted bullet that's completed encapsulated.