It breaks my heart to read that @AZ79
I do understand that you can't just leave. But I hope one day that you will.
Life is short and precious. There are many hurdles in the way. Living with someone who regularly harms you--mentally physically or financially--- is one of the most destructive situations we can ever find ourselves in. The combination of fear, guilt and uncertainty is soul destroying.
A cancer diagnosis is a catastrophe for most people. If it comes on top of personal misery think you do need help to deal with it. Best of luck. Follow your heart. Mxx