If you can rack pull at your sticking point for the same weight you failed at, then that definitely is not any sort of issue.
Try one more thing. And I only mention this just because your fail looks exactly like mine do when I fail in good form (bad form fail is bad form fail). Lower the belt on your lower back even more, put it just above your ask, and get it as tight as you can. You won't really be doing much bracing on the belt due to the position, but, for me, it removes the shake of the body and the lower back twinge and allows me to pull a shit ton more weight, the downside is it is much harder to get in a better position, but that is for me only, I'm 330 so I have a gut to deal with.
Try it on around a 85% pull with your belt where it is, then move the belt lower to where I say and see if you feel any speed increase or if it feels any easier.