It can get a bit quiet around here during the start of weekends. Some might say too quiet.
Not the best person to help you. I lift sumo and also have not been DL-ing long enough to give you the advice you need, but it looks like you are making yourself work harder than you need to with the bar. The bar is moving around too much, you can see it more as you do more reps, especially on the way down. But that’s actually good news, because once everything is tightened up, that 315 will feel like nothing.
Also on your first rep, you seemed to have engaged your shoulder blades/back, which is good, but other reps not so much. I know I have to think about setting every muscle, position, the bar, etc up all over, taking my time and breaths, again on each and every rep.
Anyway more folks around here will be able to help.