<human>: When we got engaged, he had bought the ring but not the diamond. Told me I'd get it in 3 weeks. Well 3 weeks go by and when we get to the jewelry store, he tells me he can't afford it, but I really want it (the cubic looked like crap) so we agreed to put it on my credit card and he would pay me back. He's given me over 1/3 of the money so far.  

Sadly I need to end things. I've always had my doubts but tonight confirmed it. I can't talk about anything I have concerns about without him getting defensive and blowing up. I talk calmly and he screams (and blames me for his anger and screaming) to the point a neighbor came over to ask if everything is ok. He's dilusional and thinks he "treats me like a princess" but when it comes to a discussion, he yells at me to "go the fuck to bed". I need to save myself.  

So if I end things, he will certainly know why. I fear he will be childish and not give me the rest of the money to pay off the ring so I can give it back to him. What do I do?

Give me the gist of the text in a nutshell
<bot>: Helped fiancé pay for my ring, waiting for him to pay me back but now I want to break up. How to deal with this asset we both paid for?