No worries. Here's a response to your questions:
1) You're correct about the relationship between the hips and shoulders, the back angle, and the bar's path. However, getting your butt down will incorporate more of your leg strength and be less reliant on that lower back. You're bringing them up together, but it's not at the angle you want. It'll help a number of other things that will be explained a little later in this post.
Your bar is also not traveling back when the weight leaves the ground. Instead, it's traveling straight up the shin due to your start position resembling a deadlift. This continues when you pass your knees as well. Positioning the bar over the big knuckle of the big toe, along with getting the knees forward of the bar a bit (a result of a tall chest), will help you really feel that sweep back. It's also going to limit that swing forward, which is a cause for missed lifts forward of you.
2) If you're missing 215 50% of the time, then you should be trying to hit 215 nine times out of ten CORRECTLY before attempting 225. When people prematurely jump in weight, they compound bad motor patterns. Often times, they're exaggerated even further, which will continue to drive you further down into that hole of poor technique. Could you have a great day and hit 225 without consistently hitting 215? Sure, but you won't hit again for a while.
3) Test out a new grip and see how that works for you.
Your assumption: I apologize for not addressing this with the first post, but you are swinging the bar, and it's not a result of you not properly hitting your power position. In terms of keeping your heels down and getting vertical, I think you're doing that well. I also think you're doing well with pulling under the bar. However, when people start the way you do, your hips are thrusted forward so violently that they naturally propel the bar forward rather than up. You want some contact, but not the way you're making it. The bump is made worse by the fact that you are not keeping the bar close to you after it passes your knees. Starting with the hips down and the bar a little farther away from you will help you sweep the bar back, keep it close to the thighs, and help you accelerate the bar UP rather than FORWARD by limiting that bump with the hip crease area. In all, I think this is why you're missing the majority of your lifts.
In addition to my previous recommendations, you should work on segment pulls (1", knee, hip, extend) and halting snatch deadlifts to really feel the proper bar path. I think my recommendations will help you, but you can wait to see if others have different opinions and take what you feel works best for you.
Hope that helps,
Javier A. Sanjuan
Olympus Barbell Club
Dear God, please help me lift heavy and be awesome. Thanks. Amen.