Wow!!!!!!! So much of help on this thread....Your kernel error is simply because your clocks were not stable. A very common error on Nvidia.
Also its a common known fact that when your video card clocks are too high/unstable, sometimes even though it doesnt give error, your score/FPS would turn out to be lesser. So in simple words, either bump the volts(if possible) or stay at the lower clocks where you are getting decent FPS.