Impressive weight for sure, but there is a lot going on there.
First, the safety issues.
Seeing this confirms what I was saying in the gym rats thread regarding your shoulders. You are missing a LOT of external rotation, which is most likely due to tight pecs and has nothing to do with your size. As you come out of the hole it looks like your wrists are going to snap off. There are instructions on how to fix this in the mobility thread.
My wrists and shoulders felt fine in this squatting session, no soreness, though I have had wrist soreness before, and I have noticed that lately as I've packed on upper body mass around my chest and shoulders, that my arm mobility has decreased quite a noticeable amount.
You have the bar in a har bar position, and yet because of your shoulders you don't even start with your elbows under the bar. You have poor, rounded/collapsed thoracic positioning at the top of the rep, which is exacerbated by your forward head position. Because of the amount of forward lean you get as you descend (not ideal for high bar), the weight tends to move up towards your neck. This is causing upper back rounding, which is compounded by general spinal instability. From the bottom of the rep, your unstable lumbar is evident. I looks like you're having to straighten your spine to lock out, and if this is happening here then it's definitely happening on your deadlifts.
Is har bar a typo of high bar, or actually something else? My bar positioning is an odd one for me, as I seem to have quite a protuberant lower cervical spine, which can make high bar squatting very uncomfortable for me (not on my neck before some one says it!). My lower cervical spine seems to protude more than my traps do at the back.
It's also bad practice to drop into the bottom of the rep like that, particularly when you have the above problems. People do this to develop bounce out of the hole to make it easier, but without the right positions there is a price to pay. This is also why your calves were hurting.
I think it looks like I was dropping due to the slow ascent I was making, I have dropped before, and it usually results in me losing balance, and when I'm keeping tension I can usually hear it through the floor (as odd as that might sound).
Secondly, and I'll only say this tentatively due to the difficulty of judging from that camera angle, but you don't even look to be going that deep. It seems like your 180 set is perhaps at parallel, but then it gets progressively worse. I didn't expect that given your previous comments, although it is clear why you need weight on the bar to get to the depth you train at.
I thought the same thing from viewing the videos back, though my friend who I nearly always train with assured me that I was going full depth, and he's not the type to just humour me, or say something I want to hear. If I hadn't gone full depth he'd still be smack talking me about it now.
Additionally, he moved the camera up a bit each time to make sure he could quickly spot me if I needed it.
Your issue is not a weak lower back. It's that your spine moves, putting load far more load on your erectors/lower back muscles than should be present.
I definitely have a weak lower back, I am in no doubt about that as it's been an issue for me for as long as I can remember, whether that's an issue here is another matter, though as I've said, my weak lower back is more of an issue with dead lifting.
Though it seems you're suggesting I'm sort of squatting low bar but with the bar in high bar position, is that correct?