Definitely focus on pulling back more: keep the bar literally dragging up your legs at least until your hit your knees. I've found a good way to do this is not just to pull the bar into myself but to lean back into the pull. That also helps with keeping your hips lower at the start and stops them shooting up so much.
Think in terms of between the floor and knee height you must lock your shoulders in position behind the bar. At the start this entails keeping your hips lower and not letting them shoot up so you rely on leg drive to come off the floor; this will also promote a good arch. Once the bar is off the floor it means holding that arch while your drive your hips forward and stand up.
Personally, one of the best way to learn this pattern for me was pulling sumo. You learn to lock yourself in a good starting position with low hips and shoulders behind the bar and to be patient off the floor keeping yourself in position by using your bodyweight and position to lever the bar up. The start of a conventional pull isn't quite as slow but it does feel a bit similar using leg drive and keeping your hips down.
I would also suggest slightly abridging your list of cues (which is good) to:
Hips low with shoulders behind the bar (your sit back)
Point your ribcage at the ground (your arch up and chest up)
Push off the floor fast keeping tight position'
Flexing the lats is fine, but I've found it isn't really that key compared to the others, especially if you're working on getting behind the bar. If you keep a tight, arched/neutral lower back and stay in position what you do with your lats becomes less important. I'm not saying just flop your upper back or anything, but focus more on the lower back and your overall positioning. Get that right and everything else tends to fall into place.
To get everything right, drop your load to around 60-75% and do lots and lots of pulls just to get the feel for it.