Thanks for the advice, it worked. After a bit of jiggling I could get the vang cleat to sit in the holes, then the block-and-hammer worked to tap it into place.
My mainsheet block issue was a little different. The pins and holes lined up beautifully, but the block wouldn't push forward into place. The plastic pins are basically nuts, so I tried unscrewing them and testing the mechanism with different pins screwed in. The front pin is fine, but the two back pins can't go deep enough to allow the mechanism to move. The wells that those two sit are shallower (seem to be over screws that hold the end of the toestrap). I could try screwing the toestrap screws a bit tighter to make a little more room. Then I realized it was sunny with 6-7 knots of breeze, so I sailed with the main straight from the boom - I'll figure out the main cleat next time.
I’m sure I don't have the main halyard quite right, my join really doesn't squeeze through the clew very well and it's not holding in the cleats very well (my downhaul pulls the sail down a bit rather than tensioning the luff). So I have plenty to work on.
Acceleration is fantastic. Amazing boat.