Since you are operating in slow-time domain (60Hz), there is no need for fast math; do PID using float or double precision. Divide project into independent sections: (1) RMS measurement, (2) PID control, (3) PWM output with sine modulation.
1. RMS measurement project example:
2. for PID code example, check links in this thread
3. PSoC is able to produce modulated PWM digitally - no need for using a comparator and triangulation of analog sine.
Finally, you should estimate the time budget for this endeavor realistically - this is not a weekend project.