Sf,
Ok.. You have an IC40.. this means that it is rated for a 40K pool by Pentair, but not us...

We consider it good for a 20K pool.. It is a good SWCG and plenty big enough for your pool.
Do you really have a single speed pump?? Does your pool have a Pentair automation system? Something like an EasyTouch or IntelliTouch?
Please show me several pics of your equipment pad.
If you really have a single speed pump, then you should run your cell at 100% output for 8 to 10 hours hours a day. This should generate about 4 ppm of FC (chlorine) each day..
Do NOT bring your CYA up to 70 at this time.. Bring it up to 30 or 40 now and then wait a few days and test it again. Once you get 40, then bring it up to 60.. A little at a time is better than all at once.
Thanks,
Jim R.