Am I a huge dick?

[RectalWart]

He didn't say he was "happy" about it, just felt relief. That's a human feeling, and totally not unnatural.

You didn't know the guy personally, so it is ok to feel relief that he will no longer be messing with the budding relationship you and this girl are trying to forge.

That being said, are you sure that this girl wasn't a bit obsessed with the ex-boyfriend? You did state that she talked about him all the time, even though they broke up 2 years ago. Watch the situation carefully. Try not to get your heart broken in this mess!