Pooping on the toilet

Ladies, I am in tears right now from my frustration. I CANNOT get my toddler to poop on the toilet. He absolutely refuses and cries (with tears), kicks, screams, all the above. I have sat with him in the bathroom for 30+ minutes, left him alone in the bathroom (standing outside the door) and NOTHING. I have tried everything! We have a treasure box, candy, toddler toilet, big toilet kid seat, etc. He does great with peeing, absolutely no issues there.

I NEED HELP! He has been potty training off and on for a month and strictly undies for 2 weeks. He holds his poop for 2-3 days and then when it’s time to poop, he asks for a diaper. I explain to him we need to use the potty and he just screams and cries and runs. He has pooped in his undies multiple times now, so this is not new.

What in the world can I do to get him to realize it is okay to poop on the toilet 😰