Your testing is informative. The ferrite assembly is stretching the wire tie due to the LACK of load, i.e. water on the pump side. Without water to load the motor down, the rpms are up to an unusually high speed.

IF you were to repair the assembly Id suggest that you use slow hardening epoxy on the assembly and secure it BEFORE it hardens with a fine steel or stainless steel wire wound many turns and left in place. I have done this in the past but always was looking over my shoulder for the next failure.

The highest stress point that probably cracked it in the first place, was that toothed metal hub attachment point. THat is where the force is concentrated.

Woody, good photos.