Pay the 800. It's a lot cheaper than the life you are living. There are laws protecting people living in a place----something to be aware of before you let anyone move into your house.
Sticking on this as some point you need to win only hurts you.
And, it does make me think you don't actually want him gone.
What is it you get from this relationship? (someone to blame? distraction from other problems? sometimes attention? the rush of anger?)