Your situation sounds so much like mine. I have finally left after 30 years of abuse. It feels so wonderful even though I'm lonely sometimes. Make your plans and gather your courage to forge a new & better life for you and your child.
I wish I had left years ago, but you're right, it's not that simple. You've invested your heart, time and life into the relationship. You thought you were building a life to share with the one you love, only to discover it was a sham and you've been betrayed by the one you rightfully expected would love and support you.
I am happy that you've come out of the FOG. It will be hard, but it will get better.
Find a good therapist to help you through this difficult time. Contact support agencies in your state for help in planning your escape. The YWCA often has programs for abuse victims. Also, the national abuse hotline can help you find resources to get out of a bad situation.
Here's to your better & happier future! I hope you can exit safely very soon.