I just want to add my voice to the chorus, that what you are describing sounds like abuse. I would like to encourage you to not take this too lightly.
I'm usually the type of person to encourage people to explore polyamory, to push their boundaries and open themselves to love. In this situation, you should make a concerted effort to put yourself, and your safety, ahead of either of your relationships.
I've been in an abusive situation in my past, with someone who was prone to tanrums and throwing things, but who never hit me, though there were sometimes threats. And when I chose to leave, it was a very good thing I had hidden the gun. I lived to tell the tale. I got help where I could, and got away.
And I have to tell you, it gets better. So, so much better. It's been some years, and I'm still recovering, but I would not even have been able to imagine how much happier life would be away from the abuse.
Even if you don't leave now, just make a plan. Figure out what you would need, where you would go, and who could help you. Even if you don't think you'll ever act on it, just make a plan to get out. Work out the details in your head, and hold onto that. I'm not asking you to do anything if you don't want to do it. Just make a plan, that's all.