I feel your pain,,,,Although I am not an expert like many of the people who are helping you here with the chemical advice. I will say this ...I have way to much experience cleaning up dead algae with a poor working sand filter from the days before I joined the site.

I have found that turning the filter off for a few hours and vacuuming to waste helps get rid of the "dust'. Also when I have the fine dust in my pool I use "skimmer socks' on my skimmer basket. They are expensive and a pain,,,sometimes i would wash them out a couple of times a day. They do seem to help get rid of the small particles.

If you figure out whats wrong with your filter let us know.

Good luck!!!!