The bar will bend during the dip - it should bend at the bottom of the dip just as it does in the bottom of a clean or front squat. That bend has nothing to do w the bar slipping or moving in your rack position - that movement comes from the bar not being secure enough in the rack position, which was why I told you to get it farther back.
RE being forward, watch the first 2 jrks on your first video. The 265 is good - you stay balanced on the dip and drive and you split under well, so you're under the bar and the bar is where it needs to be.
Then watch the next lift, the first missed 275. Watch the dip - you shift forward as you bend the knees, which then makes you move forward as you drive, which then makes the bar move forward and you move backward as you push against it and split. So you need to get that dip/drive balanced with the heavier weights, i.e. straight down and straight up, keeping your weight over your heels.