Relocation and Unsafe Work Conditions

I recently resigned from my position 5 months shy of my 2 years, doing so, I must pay back my relocation of $4000 because I didn't stay the full two years. Though, I ended up leaving because of various incidents, first being last year I was harassed and assaulted by a colleague I managed, It was all caught on camera and threatened my life, though I was never physically hit (you can see on camera him inches from hitting me). They never fired the employee because of the strong union and I was placed in another department and told to "stay clear" from him. I later moved to another department where my boss harassed me constantly and threatened me with bad references because I wouldn't work 6th days some weeks. I eventually obtained psychiatric help for depression and attempted suicide because of my work environment and mental health. They knew I was looking to get out and thought we would be cutting our loses, but are now trying to keep my last check of $2200+. Would this hold up in court, or would I lose based on my contract?