> Use a cut open aluminum can with a slit cut in it for a heat shield.
> Slide that behind the gear, then you can hit it with a torch.
Even using a heat shield to protect the body of the motor from direct heat, the shaft will transfer the heat to the rest of the stepper motor. Have you tried the above?
> use a socket and hammer
I’ve seen this suggestion elsewhere on the internet. And I saw the response of someone that tried it. It is a good way to damage a stepper motor. Even if you directly applying the force only to the shaft, it turns out that hitting a stepper motor shaft with a hammer results in a lot of vibrations that get transmitted to the internal workings of the stepper motor.