I have a similar spot on mine that I only noticed about 3 months after owning it. I can't see it when looking directly at the screen so it's never bothered me. I only notice the spot when I look at it from an angle and the screen is all white. Clearly it's not dead pixels, I doubt you'd be even able to see a dead pixel on a screen this size with the number of pixels that make up this screen.

I'm not sure what the dark spot is and I doubt its from the using the touch screen since my dark spot is in a place on the screen that I rarely touch and over a year later hasn't gotten any worst.