In which case you are in maintenance mode and need to keep FC between 5 and 10. If the N2 is working for you, you can stay closer to 5. Phosphates are food for algae. If you don't have algae, the phosphates do nothing. Very few here ever need phosphate removers, and those few have persistent and tough mustard algae.
I have never heard of a UV light in a pool. If it can damage the repro cycle of algae and insects more than sun light it may well break down your chlorine faster. I do not know.....