Okay -

Will turn pump back on and continue on with DE in the filter.
Will let FC go back down to normal level as there is no green anywhere in pool.

As for PAC, can I use it when I have my lower HP pump going and running on low or do I also need an additional way to slow down flow? Here is my new pump info: Pentair Optiflow 1 HP two-speed, model number 340071