The first thing to do is look at the beads in the cabinet and the trap with a microscope and see how well it separates the good beads from the broken ones. If you do it right, you should have few good beads discarded and almost all fractured ones removed. Many years ago I made a separator that worked like a cyclone separator and gave almost perfect performance. It works on the difference in aerodynamic drag of a smooth sphere and a fragment. Much of the separation was achieved by the air flowing up a not quite vertical tube with the airflow adjusted to keep the fragments airborne and the beads falling back. Unfortunately, the setup had to go to make room for other things and I didn't keep any drawings, but I recall that the final separation was done by a tilted duct with the lower part of it blanked off at the top. The lighter and aerodynamically poor fragments remained airborne and passed out above the barrier while the good beads fell to the bottom of the stream, hit the barrier, and slid back down.
I know nothing about your system but remember that a typical sandblast cabinet comes with a general purpose system that may be used for coarse grit not be optimized for finer beads.
The fracture rate of beads is controlled by pressure and the angle they strike the surface.
Bill