What's a good set of PWM values to make sine waves for a 3 phase motor?
I don't know if this helps at all but I did a little bit of work on this problem.  Harmonic Elimination PWM  It sounds exactly the same as magic sine waves.  Just thinking off the top of my head, I'd precompute a combined single table of the switching times for all 3 phases of the waveform and use a single interrupt.  As the interrupts happen, switch the particular channel then change the time until the next interrupt.  To change frequency scale the data from the table.  This shouldn't cause any problems with distortion over the frequency range you specify.  It should be fairly accurate as well given you have a 120 MHz CPU.  I had a basic version of this working on an ultrasonic transducer at 40 kHz on a 4 MHz AVR.