a few comments.
1) if you are going to spend all that money on getting those nice bumpers, spend the small amount extra and get some lifting shoes. They will help your form on squats and PC a lot and I think help with your back issues and butt wink quite a bit.
2) you are high bar squatting but you said you are doing SS. Is this intentional? Your high bar squats look decent, and with some lifting shoes I think will be fine if that is what you are going for. If you are meaning to do Rip's style low bar squat then you need to move that bar down ~3-4 inches and work on your hip drive
3) Press you are way hyper extending your back. You need to clamp down your abs big time. I have a feeling though that it is due to shoulder mobility problems. Really work your dislocates and other shoulder stretches cause that hyper extension could lead to problems down the road.
4) PC, again get lifting shoes. You are jumping your feet way to wide, and you are not receiving the bar on your shoulders. Get those elbows all the way around immediately, right now you are catching it in your hands, then transitioning to your shoulders. Stop this habit before it gets further ingrained