Oh my God, he uses black!
Yes, yes I do, even in watercolor. Works good. It's a perfectly good color if you know how to use it. I could get along without it, but it's so nice for lowering chroma, and for this black dress it's kind of a good place to start. As far as I know, no black on the market is a complete neutral. Ivory black tends to be a bit on the blue side, carbon black is a little on the warm side, but with either I find color shifts to be less of a problem than with using compliments to dull a color. If you really don't like black and find Paynes's Gray to be much more useful, you might want to check what it made with. Most manufacturers make it with ivory black.
Doesn't really matter. Color is an interesting thing and a pretty personal choice. You can usually get to a given HVC with a variety of different mixtures. One mix isn't really any better than any other as long as you come up with the color your looking for. So have a big palette or a limited palette. As long as it works for you and you know how to get the most out of it, you're good to go. Personally I've got a big drawer full of paint -- three drawers actually, one for yellows, one for reds and one for blues, greens and blacks. Most of that paint stays right there in the drawer. I find myself regularly using about a dozen go to pigments. Gets me where I want to go usually.
I didn't put a size on this. I don't have it handy to measure, but it's not very big, about 12 inches high if I remember right. It was a piece of leftover not pressed paper.