DDR stands for (D)ouble (D)ata (Rate). This is implemented by transferring data on both the rising and falling edge of the clock signal. This holds true no matter how many modules you are using. So your
clock rate of 1333 gives you 2666 effective ram speed.
Each memory module (stick) has a 64 bit wide data bus. A dual channel system will make 2 of those modules appear to be 128 bits wide. So twice as much data is transferred at a time.
It doesn't matter what speed the ram is rated for. It's only going to run as fast as the motherboard and CPU will allow. Looking at the specs
here that is as fast as it will run without overclocking which, with an Intel CPU, is called XMP. You'll see higher speeds in the specs but since they are considered overclocking there is no guarantee that the installed RAM will run at the higher speeds. Overclocking, by definition, is working outside the guaranteed specifications. Otherwise, it wouldn't be overclocking. It may work but it's not
guaranteed to work.
You are getting the highest guaranteed speed out of the ram. You'll need to experiment with XMP to get anything faster which might or might not happen.