You need to check your water chemistry more frequently in the beginning of the process. Once you add the bleach, check it again in 1 hour to see if you're at the correct level. Even in clear water with a possible (but not visible) algae bloom, your FC will drop very rapidly in the beginning as the chlorine oxidizes biologic and organic matter. I'd be willing to bet a bottle of bleach that your FC will not be 20ppm in 1hour.

Other than that, good plan. You can actually keep running the IC40 during the process, the high FC level won't hurt it. You only need to shut it off when doing an overnight chlorine loss test.

Oh, and only check FC at this point. The phenol red pH test doesn't work at FC levels greater than 10ppm.