Spock, one thing I would suggest that might help both depth and butt winking would be unracking the bar with a neutral pelvis. At the moment, you are in lumbar extension and have an anterior pelvic tilt, which is naturally shortening the space you have in your hip socket, which will cause you to go into butt wink sooner rather than later.
A nice cue that I like to use with my powerlifting athletes is to tuck their pelvis underneath them and then fully exhale followed by an inhale and 360 degree expansion (a nice feedback tool is using a belt for this and completely filling it up). This generally fixes up depth issues and actually helps with overall stability since you are able to engage the trunk and glutes more effectively.
I'll leave you this video, which illustrates the point - https://www.youtube.com/watch?v=bVjpGNkHewM (foward to 3:00 min mark).
Hope this helps!