Looking at your tank photos, they look very similar to the plant density that I had before my last rescaping. I couldn't get the BBA to stop with that much plant density.

I suggest that you just dose per EI and retire the nitrate and phosphate test kits. If you want to continue to use them, be sure to calibrate them first, using solutions you know the ppm of nitrate or phosphate in. Phosphate test kits are asked to do a very hard job - discriminating between very, very weak concentrations of phosphate in the water, and they often don't do it well. And, if the plants don't get adequate phosphate the can't use the nitrate either.