Azrayne, I don"t know you so I can"t say for sure. But I think most often, when a guy doesn"t want to break it off with an unstable girl, it"s because he simply likes the affection.
One of my best friends is dating a girl who is, rationally, a soul-stealing succubus, but he can"t let her go even after she went total psycho mode on him. Previous to that he dated a girl who also went psycho and lived in another state and neither had any intention on moving, yet he didn"t want to break it off. I talked to a girl for months that I met on spring break once, we lived 10 hours apart and I absolutely knew the "bond" we both felt at the time was an accident of the situation and we really were way too different. In all 3 situations, I know for a fact it is/was just the attention and affection that kept the guy (my friend, my friend, me, respectively) from breaking it off.
It"s dangerous though. You think you are detached and guarded, but you can"t be completely. When she finds a new flavor of the month, as these types of girls do, she"ll drop you without warning and you will realize you had come to like and depend on the affection from her. I made the mistake of being friends with a girl like that, yes even FRIENDS and on MY terms, and despite keeping myself at a distance, when she found a new boyfriend she bailed on my big birthday party even though I was moving away barely a week afterwards. And I was pretty pissed about it even though I specifically made a point to keep myself at a certain distance from her since I knew how she was.
There are times that your reason and your emotions are at odds. And while there may be the rare occasion, I"ve never actually seen or heard about a situation where the emotional desire turned out to be the right call. It almost never is. If you break it off asap you"re gonna be happy you did later, I can almost guarantee it.