It will be running at 1600mhz, cpu - z just reads the base speed of the memory and for 1600mhz that will be 800, remember DDR = Double data rate.
So therefore double your base rate 800 by 2 and u get 1600mhz, so no need to worry, it is confusing abit if u don't know how cpu-z reads it, but your fine.
About the max bandwidth thing, that again needs to be doubled so it would be 1333/4 that is the fastest official speed for DDR3, anything above that is overclocked modules now this just means when they made the modules some would run a lot faster, so they sell them at faster speeds. Again its nothing to worry about.
Cpu-z states ur running at 800mhz, which equates to 1600mhz so your memory is running at its rated speed.