I'm still of the opinion that ataraxia has to do specifically with rooting the fundamental causes of fear and anxiety, ie, death, divine punishment, etc. I don't see one who has ataraxia as never ever being afraid of anything, never ever being anxious about some aspect of life. But the root causes of existential dread, fear, anxiety, once those are torn out - root and branch - they don't return and one has an unshakable foundation upon which to build one's life.
Something similar could be going on with aponia. How that works, I'm not exactly sure - Epicurus definitely uses it to refer to physical and mental pain, but I drop this here as a prompt for discussion.