Do I have legal rights against a verbally and psychologically abusive boss?

I've been working for an internet-based home office company since January of this year. Over the past 4 months, my boss has become both verbally and psychologically abusive to me. He had always had emotional outbursts, but then he started directing them toward me. Both myself and the other girl in the office had told him that when he raised his voice, it made us freeze up and it also made us fear for our lives. He responded with that it was just his nature, being part-Italian and he went right back to yelling. He began triggering his comments toward me, jumping on every single thing I did. At first, it seemed like he felt some remorse, but after a week or so, the gloves were off. He'd verbally attack me and when I didn't respond, he'd knuckle punch me in my shoulder blade or arm. He continued to attack me verbally and would occassionally raise his voice to the other employee, but it seemed because he only had 2 employees, he needed to be on her good side. He began psychologically wearing me down, attacking my character and my integrity, so much so that I was speechless and just sat there crying--and still he would continue to attack me. He's also, on several occassions, blocked the exit to the office and kept me after hours to continue to yell at me. He threatens me with legal action against me if I quit, but I can't take it any more. Both myself and the other girl at the office are constantly on the verge of tears. When I ask him calmly to lower his voice, he refuses and tells me I can't tell him what to do because he's the boss. While I'm seated, he'll stand over me and so close to me that I can't stand up. I just can't take the verbal abuse anymore, it's taken such an emotional toll on me that I can't sleep at night, I have constant headaches, and I can't function properly at work because I'm terrified of this man. If someone could help me and tell me if there's anything I can do, I would appreciate it greatly.