Very good advice - most of the sand-living organisms are very fragile, and the sand grains can actually cut or crush them if the sand is moved forcibly. Also, many of the sand-living worms actually build tubes by "gluing" the sand granules together - if the sand is disturbed at all the tubes will bread, leaving the worms exposed to predators, etc.
See it this way: the detritus that has fallen to the floor of the sand bed is being eaten by the little critters - why do you want to suspend this in the water column again, where it will be pumped back to the display tank???
WOW, that NO3 and PO4 values are VERY high, and will certainly not be good for your corals. With the dsb being 2.5 months old, I would suggest that it has not fully matured yet, and that your bio-load should be kept very light at the moment. Use GFO phosphate remover and grow whatever macro algae you can find in the sump, to try and reduce these two parameters. Are you not perhaps using an aerobic filter (fluidised sand filter, canister filter, trickle filter, under-gravel filter, etc.) in your system? If so, that will explain the high NO3 level.
Hennie