Geez Louise. This sounds way too much like "Hi. I'm here to give you this gift. I'm going to ram it down your throat."
As to his sponsor, it sounds like your ex is twisting the words...
He goes on to explain that his sponsor has been inquiring with him about whether or not he has tried to reach out to me
His sponsor didn't ask if you accepted his amends, he merely asked him if he already reached out to you. If yes, OK, he did it. If no, well he should...
since a lot of his "self hatred and resentment" stems from the abuse and trauma he put me through in our relationship."
That's the reason why he should seek, NOT FORCE, amends from you in the first place. Whether or not you accept the amends is totally up to you. To me, at least the way I read it, it's NOT a reason to badger you into accepting the amends.
The way he's behaving now, he's generating resentment in spades.
Just a suggestion, I would set a filter to send his email straight to trash.