Can I control 2 NXT bricks from a computer using bluetooth at the same time?
Yes, this is definitely possible! You can connect up to 7 different NXT devices from one computer and one Bluetooth dongle (theoretical limit). I have tested this with the RWTH - Mindstorms NXT Toolbox for MATLAB) successfully with 5 NXTs on Linux and with at least 2 NXTs on Windows. 

In real life, it depends on your Bluetooth hardware. Your Bluetooth stack or driver software should provide several serial COM-ports. You can then connect each virtual serial port to a seperate NXT device, and access them via those different serial ports. 

If you go the direct way via the official LEGO NXT Bluetooth SDK you mentioned, you can retrieve different handles to multiple NXTs.

Oh, and for the record: You can also connect multiple NXTs via USB, and you can also mix and match with Blueooth.

Regards, Linus