You are getting good advice = keep hitting it with bleach. You need to test 3x a day if at all possible (at the minimum twice a day) and each time, add enough bleach to get back up to 10ppm. If you let the chlorine level bounce up and down, you'll never kill the algae. To make your test kit read higher, dilute your sample. Mix one part pool water and one part distilled water, test as usual, multiply your result by 2. If you still need to go higher, one part pool water, two parts distilled, multiply by 3, etc. Each time you dilute, you lose some accuracy, but it will be better than nothing. Consider buying the test kit from Ben. Well worth it.

I would hold off on adding any stabilizer (cya) until you have the algae problem solved.