Thanks. I've wondered the same about my stance width, so I'll try experimenting with a slightly narrower stance. Getting the bar to the right spot on my back has always been an issue due to my tight shoulders. It's gradually making it's way down as I squat more, so hopefully will get there eventually!
Low Bar Position Stretch | Paul Horn
Also do shoulder dislocations.
I also fixed my depth issues by setting a small box or medicine ball under me for warm up sets only. (DO NOT! put any weight on it. Just stay tight and touch it.) The point is to use it as a depth gage to develop the bodily awareness of what the proper depth is prior to the work sets, don't get too accustomed to it being there or it will cause problems.
You do need to go lower but your bigger concern is your back angle. It's way too vertical. You need to bend over a lot more. "Point your nipples at the ground!" Also stop looking in the mirror. Look down. That should help with your back angle as well.
I'll just say that giving him advice to bend over more when the bar is in high-bar position isn't going to work. If you look at the first two reps, his weight is over his mid foot and the bar stays in a pretty good vertical slot. Bending over more before getting the bar down into low-bar is going to throw that balance off.
As you work the bar lower by following Charles' advice, you'll need to bend over more with each adjustment in bar placement. You've got a good feel for mid-foot, just be sure not to lose sight of that, above all.
As for depth, I like Brian's suggestions, but I'd also say you should try taking a little weight off the bar too. I did a 10% deload when TomCampitelli was helping me get lower (though I discovered my main issue was that my sweatpants were mucking up my sensory feedback, making me think I was lower than I was) and it helped lock it in.