I went back to the beginning of the powder measure setup, the die needed to be screwed nearly all the way down (within a quarter inch of remaining threads) before the powder measure run the complete travel. I adjusted it carefully to right about where it made full travel, then tightened the die nut.
At this point, when I ran a casing through it, the primer seated perfectly and the case went up and came back down without fuss, but it had too much flare/belling on it. So I loosened the nut on the primer die, and turned it to raise it back up about a 16th of a turn, and put another case through it. This time the flare/belling was twice as much as before. I thought, maybe it needed to seat/settle in, so I tried another, same thing. So I loosened the nut again, turned it to raise the die another 16th, and this time the casing was completely stuck. When I finally got the lever back up again, lowering the shell plate and the casing, the casing was radically flared, the top was shaved half off, and my fun-meter was about pegged out.
So my question is... apparently, raising the powder die (so that the powder drop sits higher off the top of the toolhead) causes MORE flare/belling, not less? That seems counter-intuitive, but if you guys confirm it, I'll adjust in the other direction.