How to generate random data with a specific bandwidth
In the case of BPSK, the data rate equals the symbol rate (one bit per symbol). One way to control $R_S$ is to change the modulation. For example, you can increase the number of bits per symbol by choosing a higher order modulation like 16-QAM which has 4 bits per symbol. 
There is nothing wrong with your calculation. The plot is a single sided spectrum so you only see half the bandwidth. It roughly dies off around half of 1.35 MHz so assuming your code is correct, I see nothing particularly wrong with the plot or calculation.