Wow...for a nano tank you have lots of stuffs going on - chiller, sump and all. Seems like a lot of work to me. Guess it is needed as you are keeping SPS corals, said to be more demanding than LPS.
Read your earlier post on attempting a tear-drop clam. I havent had much success with clams, they always wither off after a while, even when i feed them with plankton and stuffs. I'm not sure if it is due to the temperature, but then again, my LPS are blooming.
Continue using your PO4 recommended by Henry. He's a helpful chap and i love talking to him to get some tips. The other product that i use is Reef Biofuel by Brightwell, which helps to further reduce phosphate and nitrate.
Try to keep your pH to above 8 as this will help in corals and fish species. I top up my tank daily with Alkali water with pH10, to ensure that my tank pH is kept consistently between 8-8.5. Reasons of lowering pH is due to overfeeding, wastes etc.
Like you, i have my own trials and errors, and usually the error results from overseas trips. Lots of $$$ goes into this hobby but the feeling of success is priceless. You can read about my tank journey here...