I think I've discovered a trick to get the disc pivot feeling in the first drill...
...I've been able to get a very strong feeling for the disc pivot in the first drill (the one where the arm and disc fall downward) while messing around today with a Teebird while talking on the phone. It surprised me, but I knew it when I felt it. The key was in the way that I was holding the disc: my index finger tip and middle finger tips are pressed against the inside of the rim, and my finger nails are on the bottom of the flight plate. My thumb lightly presses on the top of the flight plate (but close to the rim), but this is very loosely held and only serves to keep the disc from falling off my index and middle fingers. This loose grip enhances the pivot, and makes it really easy to get the feel for it. And very easy on your fingers, too. The timing is everything. You have to find out when exactly to apply downward force, and how much. I think I'm applying a little force about halfway through the fall, and then everything seems to fall into place. When I look back at Blake's videos, I recognize the timing and how this all fits.
Next I'm going to work on the fake grip again, since I think this is still critical for getting the feel for timing the pinch correctly, in addition to feeling the pivot. Note that I've felt this pivot before when driving backhand, while pressing in against the rim with the same fingers in a similar manner. I just need to get this feeling going when I'm also gripping the disc like crazy.
And then I need to feel the pivot with a proper sidearm orientation, and do some field practice. Man, I'd love to get my forehand throw back in shape again!