Re thermal paste I would just look up the temperature operating range spec for the stuff to make sure it was intended to be happy doing kettle duty + some comfortable margin of error.
I'm not at all worried for performance, moreso for your health. Wouldn't want that shiet burning and outgassing and giving you cancer or something, wafting through your kitchen
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Try googling for thermal paste intended for espresso machines? That might be a fit for your application.