The main reason for using filler in end pours is to replace some of the heavy, expensive epoxy with something lighter and cheaper (sawdust, microballoons) Since your dust is epoxy it won't save any weight although it will save fresh epoxy.

I am intrigued with the idea of using the dust as a filler to thicken epoxy for gluing.

On the subject of the toxic characteristics of this dust: If the epoxy is less than fully cured the dust can be really dangerous.