I've never dealt with this before (a car that the front end chatters teeth but only under acceleration) and it's been hard to figure out so far.

I didn't know a CV joint could make the front end shake. I was advised, offline advice, to check the balance weight on the long driver's side axle and it was there. I was told that if it falls off it could cause a harsh vibration. The weight is still there. What I'll have to do, and should have done in the first place, is get the car on a lift or lifted up on both front and check everything.

The rotor is badly grooved and I suspect it's warped as well, as per my "brake pads" post. The vibration is only under moderate/hard braking.