PO4 at 2.0 is very high. that is definitely part of your problem.
i noticed when i had high PO4, and just threw some bags of PO4 removal media into the semp, basically nothing happened. however, when i put the media in a reactor, it is MUCH more effective at removing the PO4. however, it still takes time so be patient. test the PO4 every 2 days or so to see what happens.
also, if your tank is old, or the LR was purchased used from somebody else's tank, it could have absorbed it's quota of PO4, and can no longer absorb any more, leading to a build up of PO4 in the water column. that is the common "old tank syndrome" that people used to complain about it. if that's the case, you can add new LR, or switch out some of your LR for fresh pieces.
also cyano is not the only reddish macro-algae out there, just the most common. take a look for some pictures to make sure that is what you have. also answer the first responder's questions.