A working DE filter is going to get all the particles -- by itself -- that polyquat or a stronger clarifer would help with.

I think your best chance of cleaning the pool is to raise your FC to 20 ppm, and keep it there, till the pool clears. With a CYA=100, 20 ppm is NOT too high, even for swimming.

By the way, use the 10mL sample with your K2006 -- you don't need to measure to the nearest 0.2 ppm -- and your reagents will last longer. Also, if you get full color with the first dropper of powder, you don't need to add a 2nd dropper.

The OTHER thing you might do is to disassemble your filter (I assume it's a Perflex) and clean it fully. Unless the fingers have scale on them, simply spraying them off will be enough. Wear your OLD swim suit for this; it tends to be a nasty task.

This video illustrates the task well, except for the fact that they are using a clean filter and recommend an un-needed proprietary cleaner. If you DO need to clean the filter, you can use an plain powdered laundry detergent + a cup of bleach. If scale is present, you WILL use muriatic acid 1 gallon to 5 gallons in the 2nd pass, but ONLY if there is scale and ONLY if you have first cleaned and degreased it. (Hayward manual)