Hey everyone, brief update. Things went a lot better than usual. This is what went down.
After reading the thread, we decided we should probably try to kick him out without bringing up past issues. He defended his actions (cat abuse, drug deals, etc) tooth and nail. So, we decided to find a ploy to get him out. He came by the other day, and I said "Hey, we're going to move the weight rack in the garage into your room since the room is virtually unused anyway," He agreed and I figured it was implied he was done. He left, and I forgot to ask for the keys. When he came back the next day, I asked for the keys, and he left while I was in the john.
I finally got a hold of him just a bit ago via telephone to clear up some stuff. I told him that he wasn't really around and we wanted to use that room. And since he never stayed there, I figured it wasn't going to be a big deal. I asked if we were cool, and he was a little wishy-washy. He seemed to start pouting, and quickly ended the conversation.
We still don't have the keys, but after consulting with a few people, we are able to change the locks without issue.