Hello-
You are actually doing a decent job getting your knees out to the position of your stance... but your stance has your toe angle too shallow. This is why your squat is pitching onto your toes as well. The stance does not allow for enough knees out, which is keeping your femurs in the way.
Here is a picture from the SS book showing the toe angles.... Try taking a little bit more toe out- and then shove your knees out to meet this toe angle. You will feel like your femurs are much more abducted or spread apart, but this will help you do balance your weight over your feel in the whole and sit back.
Toes_out_images 2.jpg
Keep training! You will have a strong squat!