Does Bluetooth range increase with lower baud rate?
In my experience, radio modules usually have 2 different baud rates:


UART baud rate is the baud rate for communicating to microcontroller on the board. Usually, it's adjustable.
Over-the-air baud rate is the baud rate for communicating via Bluetooth.  It's usually fixed.


I've searched through the user manual and datasheet for RN-41, which is the Bluetooth module inside the dongle.  I didn't find any indication that over-the-air baud rate is adjustable in this module.

So, I doubt that you will get more range if you configure the baud rate down to 1200.