I dunno, reward was 15 XPM yesterday.
Block reward is 999/diff^2.
Each whole number difficulty increase is a 30x increase in the amount of network power required to maintain the same block rate. Good luck reaching 810000x network power for a little while without ASICs. GPU miners won't get anywhere near that amount. Someone already explained why GPU mining is a 10x at best (and that's with CUDA), and because of VPS deployments GPU miners won't even make a dent in the network power since you'd have to buy new hardware.
Care to elaborate more on this, I can't seem to follow your math.