For a variable speed drive, you would use pwm to generate an approximate sine waveform on three phases. To limit the current, you simply generate a sine with less voltage - this is fairly simple to do since your code is generating the sine waves. You software example has a major flaw in that the delays won't be consistant unless you ensure the delay through each path of your code is the same - hard work, so that's why you use specific micros with the correct hardware features for this application.

You need to do some research on this subject - check out app notes from Atmel and Microchip ( amongst others)