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Warnings are good.. table saws are the worst... Whichever direction things go, there seems to be very heavy forces bearing down on this little gear.

Looking at the way the original worm cracked, splitting almost exactly in two, it appears weakest where it is deeply slotted for the split-pin.
And the hex-recess on the other end (which serves no purpose) contributes 6 sharp inside corners, which can propagate cracking.

Did the worm split exactly at two of those hex corners?

A new factory part will likely be identical. (cast pot-metal from the look of the mold ejector-pin indentations)

Maybe a metal washer over the pin-end, behind the pin, would prevent the catastrophic split-in-two.
Not much you can do. A steel gear would solve it, but I doubt it will be easy to find one.