Think a bit on what is in the dust. They shed bits of skin and bits of down, called dander. If the brooder is dry their scratching shreds bits of the bedding to dust. When their poop dries out their scratching turns it to dust. A wet brooder is unhealthy, you really want to to be dry. So some dust will be there from the start but the bigger they get the more dust you see.When does the dust creation of chicks start? Would they not be so messy for a week or two? Or is it a dusty mess from the beginning?
Have you tried putting a thermometer directly under the lamp to see how warm it gets in the different positions? Put it chick high, not on the floor. Checking the far end would be good info too. You want it to cool off some. Of course, their behavior tells you more than any thermometer.
That chicken wire lid creates an issue raising and lowering the lamp. My brooder is in the coop. I built a chimney out of wood so I could raise and lower the lamp as required. The chimney itself never got that hot but I kept the bottom of the lamp below the bottom of the chimney.
I don't know where you are located but you probably have your chicks by now. Good luck with them.