For a CYA that high, your chlorine needs to stay in the 8-15 ppm range. I personally would keep it closer to 10 ppm, to allow yourself a little wiggle-room, but you don't want it drop drop below 8 ppm at all.

If your water is clear, and unless you need it for the heat pump, you don't really need to run the filter for that long everyday unless you just want to--you'd save yourself some $$ on the electric bill if you cut it back to 10-12 hours/day, and even that is excessive for some pools......