Those Cl levels seem so high for safe swimming.
I had a very similar problem this year fighting some green algae that seemed to be unable to be killed by Cl well above 10 and all other numbers in the "normal" range. My solution was to create a 3% solution of Copper Sulfate and add 500 mL to the pool. The next day the pool looked great - a little cloudy (Calcium Sulfate is all but insoluble). Cl over the week fell to 3 and water was beautiful. After a month of shocking and vacuuming daily, this was such an easy fix.
Why is Cu so frowned upon when it can keep chemical usage so low?? To me this seems safer than high Cl levels.
20k volume vinyl inground pool, sand filter, 1hp pump