Read the CURRENT 3rd edition of the book. The information you have is outdated.
That point aside, you need a coach.
1) Do NOT face a mirror.
2) Look DOWN at the floor, roughly 4-5' in front of you. This means both the eyes and head angle are set and constant. It should look and feel like you are trying to hold a tennis ball under your chin.
3) The bar is in the wrong position. It should sit underneath the spine of the scapulae, viced in tightly between the bottom of the spine of the scapulae and the top of the posterior deltoids. Grab the back of your shoulder and use your fingers to palpate, walking your fingers outwards to locate the acromion process (
https://en.wikipedia.org/wiki/Acromion). This is the terminus and most prominent part of that spine. The bar sits at the BOTTOM of that part of your body.
4) Your grip is too narrow AND the bar is sitting too high in your hand AND your wrist is bent.
5) Neither of you guys are squatting below parallel. An above parallel squat is not a squat.
That's enough things to fix all at once. You will have other issues after these issues are fixed.
Most importantly, you need to
read the current edition.