I have been dealing with a nuisance nutrient issue for about 4 months. After exhausting quite a few avenues to control/stop algae and cynabacteria growth, I have determined that my live rock is leaching phosphate. My corals started florishing right around the point where I experienced cyanobacteria and green hair algae blooms. At some point I'd like to add a durasa. My questions are as follows:

1. Do you have a practice for determining how to regulate nutrients to an optimum level? I imagine that immediately after installation, the algae scrubber will help me export the phosphate leaching from the live rock however I will need to start 'dosing' nutrients through food cubes / coral food over time, when the phosphates have all leached, to keep the coral thriving and to enable the addition of a durasa.

2. I get the basic concept that I cannot 'over-scrub' however there have to be some limitations to scrubbing. I'm considering the HOG scrubbers as my sump space will only allow for that type of configuration. How do I establish a reasonable bio-load limit? How do other filtration elements such as GAC or skimming work in concert or become irrelevant to maintaining a certain bio-load in the tank?

3. Are there any considerations for things such as tank lighting or water circulation through tank and sump after algae scrubber installation?

My setup:
45 Gallon Tank + 5 Gallon Sump (~35 Gallons of water)
5 small fish and a cleanup crew of crabs & snails that get about a half a cube of food a day
Small to medium sized colonies of Octospawn, Gonipora, monipora, zooanthids and mushrooms
Currently suspended coral food