Mostly I feel this way (I think) is because in "normal" situations if relationships don't work out people work through that part too, or they part as friends, or they give it their best shot, or they take a break and come back or something.
Boo,
Plenty of relationships just end...and badly. You can't make him "work through" anything. You can't make him "part as friends"
You are causing yourself pain here and you are free to stop at anytime.
I have had guys in my past who, like you, simply would not take "no" for an answer. In fact my alcoholic son is one of them today. It makes me feel trapped and I come out swinging.
If you refuse to let this guy go then you better be ready to duck!
JT