First, it aint all that bad as it is.
Kinda tough to diagnose because there's so many settings that affect each other.
Things I'd try one at at time:
- Match FPS and Iframe - both 15
- Humor me and bump bitrate to 8192
- Backlight may be part of the problem. Try with it off
- Try 1/30 and 1/60 with Backlight off. about 0-50 Gain
- DNR as low as you can stand, but you dont have much noise
- Play with that Gamma setting a bit, Ive rarely moved it from default 50 with any success...