Hi there - On your CYA reading that appears to be 45, round your CYA result up to the next ten. So if you think you see 45, you should interpret that results as 50.
Your chlorine levels are hard to understand because you haven’t listed when you’re actually adding chlorine. For example, your FC readings are increasing in the evenings, which is very counterintuitive. When I look at your results, I see the FC bouncing up and down but without knowing when you added chlorine and what the FC level was after that, personally I haven’t tell if you’re making progress.
Also, are you actually testing your water after adding the chlorine to confirm that you’re reaching 20 ppm? Or are you adding a certain amount of chlorine that you believe will get you to 20 ppm and assuming that you’re reaching 20 ppm? You should test the FC level maybe 15-20 minutes after adding chlorine to confirm you’re reaching 20 ppm.