He might leave willingly, but since both of your names are on the lease the apartment and its contents are joint property. He could get totally rageful, take everything that's not nailed down, wreck the apartment from top to bottom and you probably wouldn't have any legal recourse at all.
Not a legal expert of anything here, just playing devil's advocate - sorry if it seems harsh. But for your own sake, you need to legally protect yourself as soon as possible.