I don't make it a habit of giving advice on the internet, but since you asked...here are my suggestions for improving your form. I can't promise it will make you any faster, but it made me faster.
Preface: This is always much easier to show someone when they are on their own bike on a rear stand. Body position in pic 1 and 2 are significantly different from 3 IMO. However, pic 3 helps explain some of the issues in 1 and 2.
1. Get your butt back. Not severe, but to begin with will feel severe. Really you only need to slide back a few inches in order to set the rest of your body properly. This will help with #2. This will also flatten out your torso so you're not so hunching over. And yes, one cheek should be plenty until you have corrected some other isues and develop your own personal preference after some seat time.
2. Refer to pic 1 and 3. In pic 1 your hip is open and you are sitting like a frog. Likewise, (note the direction of your pelvis) your upper body is inline with the left side of your windscreen. Whereas in pic 3 your lower body (note the direction of pelvis again) is pointing toward your outside clip-on. This is naturally causing your torso to head in that direction. After addressing point 1 open your inside hip and turn your leg out. This will help to align your upper body.
With the seating corrections, you most likely won't have the ability to stick that outside leg out like a wing anymore. However, if so, I suggest putting it up against the bike to assist you in going back to tuck smoothly. Smooth inputs...mmmm good.
3. The guys who have helped me get faster have a mantra when instructing...try dragging your helmet and not your knee. After a few laps of getting comfortable with the above changes, get your head down as low as you can. No seriously, as low as you can. So yeah, I too say get your head down. Combined with the above changes your torso will be aligned and COG will be lower.
Take my free advice for what you will. Hopefully, you'll try these changes and feel much better on you bike. I know I did. Worse case scenerio is you've wasted a few laps trying to improve your body positioning at a trackday.
These pictures of Stoner is a good illustrationof the alignmenment I try to acheive. Note the direction of his pelvis, Opened up hip in pic 1, and alignment of his torso in pic 2.