Also L5S1 two time discetomy patient here, so yes I hear you on the worry for this, and it does matter for those who may chime in after as it leaves you particularly vulnerable to poor form causing further problems.
Observations in no particular order for what its worth:
#1 - watch your bar path, you’ll notice it is drifting quiet far out in front of you on the way down in these videos, this increases leverage on lower back
#2 - You may want to get two medicine balls, or some sort of wooden block setup 8" off the floor so that you know where the “bottom” is. A standard bumper plate is 17.2" is diameter with a 2" insert for the barbell. That’s where I’m getting the math from. This will ensure you’re not going too low in your lift
#3 - when you setup, barbell should be at mid-laces on your shoes and go straight up. Depending on height (for others) this should JUST clear your knees on the way up. You can tell from your vid that your bar is too far forward given the space between knee and barbell.
#4 - Keep your speed consistent up and down. You dont need to rocket up, try and keep things moving at the same speed and hold form throughout.