Help from experts here on form doing SL 5x5 B workout

I would suggest asking in here Eat, Train, Progress

In both your deadlift and squat, your low back is rounding. It's a lot more obvious in your DL, but I can see it slightly in your squat as well. Looks like a core bracing issue to me. You are not properly bracing your core so your lumbar is rounding. The lumbar should be neutral at all times. Once your core is properly braced and locked in..the lumbar should not flex in either direction. Must remain neutral and stable at all times. Sounds very repetitive, I know. But I'm trying to drive the point here.

Watch this to learn how to brace properly:
https://www.youtube.com/watch?v=_StSjmX1BOg

Also..do you have flat feet or are you known to overpronate? Looking at your deadlift video from the front, it appears that your feet/ankles roll in. When your feet collapse, everything falls out of alignment. The knees collapse as well (look at the 10-15 sec mark in your front-facing video) and your glutes/hamstrings don't engage as they should. Your glutes not working like they should is the reason your deadlift looks like you're just yanking the weight up with your back, as opposed to using your glutes and hamstrings to move it.

More on core bracing here (from 1:00-6:45):
https://www.youtube.com/watch?v=U5zrloYWwxw

If you want to fix the foot issue.. focus on maintaining 3 points of contact with the floor.. big toe, little toe, heel. Then screw your foot into the ground: http://www.marktosques.com/posture/stance/getting-tight/screw/

Or some say focus on pushing from the outside of your foot because that also keeps your feet from collapsing.

Personally for me the 3 points of contact + screw foot cue works better.

Anyway. Those are the only two issues I'd work on for the time being.

add a big grain of salt to all this, but . . .

squats: i'm scared to comment on squats since my own form is all over the place atm. only two thoughts that might be helpful: you seem to stay tipped a bit forward the whole time, bum back and chest forward. maybe concentrate a bit on a bigger glute squeeze from the back and bracing your core from the front to bring your whole body into better alignment directly under the bar before actually starting each rep?

ohp:
- in the first set it looked to me like you were still settling your grip at the top of the first rep? i think i see your right fingers sort of flickering around up there. i do this too, but you might want to try giving more time purely to taking your grip even before you unrack.
- second ohp set (from the front) it looked like you had the bar way back in your hands. dk about you but that really gives me the ows if i forget to make sure i've got it stacked directly over my elbows/wrists, i.e. more in the heel of my hands. ohp is a struggle for me, but i do notice it goes much better if i invest time in really getting the grip part locked in and everything from my armpits up tight even before i unrack. it looked to me like you were rushing that part.
- also think that during your first set you got better and better at locking it all the way out at the top. your head seems to get a little more 'through' the arms with each rep. was it feeling more fluid as you went along? that's the impression i got from that set.

deadlifts:
- definitely when i'm deadlifting i spend a bit more time pulling myself 'down' to the bar before starting the pull. idk what the more technical term for that would be. but it doesn't look like you're giving your back a good chance to really do what it could. it also looks like you're not pulling the bar 'in' toward your legs/getting your shins to the bar. i try to kind of spread the weight of the bar through my entire body to start with, and only pull when i feel like i've got that part of it sorted out.