You have a lot going on there, you don’t sound over stocked wich is good.
How much rock do you have?
How deeps your sand?
How longs it been set up?
How much are you feeding?
Depending on those answers this is what I would do.
Remove the macro algae, it won’t grow very well with nitrate that high so will die and re release nutrients back in to the water. Also if your iron and iodine levels are low that will stunt its growth.
Keep going with the carbon dosing and maybe up the dose, if I know what your dosing and how much I could give you a dosing figure. Keep the skimmer clean and skim very wet, at least a full cup of tea skim a day, make sure to keep a eye on your salinity as very wet skimming can make it drop.
If you get a bacteria bloom you have gone to high with the dose so back it off.
If the nitrates don’t go down the best way to add phosphate is chuck a cube of frozen food in.
I’ve probably missed something so ask any questions