Let's be realistic here, he lives in your house because at least for a time, you allowed him to do so. That it turned out to be less than ideal for you is something that happens in relationships. But I will not speak to what quality of person your bf is because only you know this. Let's not make the fact that he lives there all on him. Clearly you had a part in making that happen so yes, at this point you've realized he's costing you a lot of money with nothing in return but you weren't innocent in getting everything to the point it is now. You had a hand in it too.

Look at it this way if the $900 is making you choke. It's not entirely going to make you feel better but maybe a little. its either $900 now and be free of all the costs going forward which I imagine will far surpass that amount or endure more costly expenses as he continues to leech off of you.