You are on the right track. But you need better test tools.

If you can get an OTO test kit that goes to 5ppm. If you can, get one from Taylor or, possibly Leslies. You'll need to look up the "CarlD Patented Shot Glass Method" for getting your kit to read to 10, 15 or even 20ppm (You'll need steam distilled water--avail at the supermarket).

For pH you are probably not getting an accurate read due to your high chlorine. If you get the Taylor/Leslie's kit, look for the red bottle to be 0014, not 0004. Or you have to get a chem called chlorine neutralizer (Taylor R-0007) and put 2 drops in the water before adding the red stuff.

Otherwise, read our thread on battling algae. You are not far off!