"I can't leave them because they threaten to hurt themselves if i do" is bullshit.

And I think you know this deep down.

This is the most obvious use of your empathy as a tool for manipulation. Only someone who doesn't care for you at all could do this.

Anyone with an ounce of empathy knows that this is a line you don't cross. It's the most selfish thing I can think of.

You aren't responsible for their mental health. Call the police immediately and make sure they spend a couple days in close psychiatric observation. Someone who threatens this is obviously unwell and needs help.

Along the same lines of thinking, you ARE responsible for YOUR OWN mental health. You are allowed to protect yourself from abuse, and you absolutely should.