Hi Phil,
Your picture of the egg shaped vertical test pattern reminded me of the issue I had with my Stewart Warner 9100 mirror lid set. In order to correct it in my case I made a change to the RC time constant in the plate circuit of the vertical blocking oscillator. The original per Sams' was a 0.15mfd cap and a 2200 ohm resistor. I ended up using a 0.1mfd and 330 ohm resistor to get a balanced ellipse vertically. Increasing the width adjustment then made the the image circular.
You made great progress.
Ed