Some of my first thoughts are that - you're both young, and he had said that he wanted to break up (repeatedly he said that), and he doesn't know what he wants. And you describe your arguments, and behaviour (throwing things, slapping him) - why would he want to date someone who does this? So - after she says no to him, then he figures that he doesn't want to give up what he's got with you. What is it that you love about him? Do you both need some space from each other? What would you hope to change?