Bob: Welcome to the rotozip world! Looks like you cut 1/4 MDF ( 3rd pix ). What size bit? Suggestions: The 1/8" inch bits are pretty fragile and flex easy. That flex causes the breakage. Best bet is to keep the rotozip perpendicular to the work as much as possible and only just enough bit sticking through the material to make the cut. Ya, there are times... Some bits are not fluted all the way to the tip: a fence kinda, so watch for that. Always work the rotozip clockwise and don't force it, let it gnaw the material as it can. Bit speed is another consideration. Too slow and you have a bucking horse, too fast and you have burn marks. Inbetween those, you are pretty much cutting butter. You might even get a thicker bit. I use 1/4" for any material thicker than 3/16". I have done 5/8" ply with a rotozip, but it is an exercise of patience/frustration and pretty slow going. Plunge router would be better, but then you have logistic problems with the circular base.
I have enjoyed your layout progress - keep up the great work!
L8r