It does sound like he isn't going to be moving out anytime soon. Deep down, your parents may even kind of want him to always be there. This sounds like an environment that you are not going to feel happy in. Getting established as an independent person with your own residence can be tough, but you will be motivated to put in the effort that it takes.

Meanwhile, if he physically attacks you, that is against the law. It is also against the law to threaten another person with physical harm. Should that happen, you can call the police. You can always go and fill out a police report about any incident like this that occurs.