Emma,
Tell him if it serves you, not if it doesn't.
I knew what I wanted/needed to do ages before I could actually figure out how to do it.
What helped me:
1. reconnecting with friends who I spent a lot of time with during the parts of my life where I felt the strongest. Talking to them, and my family, about some of this stuff. That made me realize I had a net.
2. This forum - this forum has been HUGE for me. The first clear demonstration that I am not alone in this struggle, that just maybe I am not a defective person, just in a dysfunctional situation.
3. Going to an Al-Anon meeting. Sitting in a circle with a bunch of other ordinary looking people telling their stories, any one of which described my life. I realized I had an even bigger net.
I did not tell my AH that I was going because I didn't want to, and I decided it was none of his business.
Afterward, I felt so good about the experience that I did tell him, and suggested he try AA, because I had been so buoyed my my own experience with Al-Anon. I felt like it would be ungenerous of me not to encourage him to go once I realized how valuable it was. I'm glad I did. He went once, of course, and decided it was not for him, he could not relate to those people, he'd never been homeless etc... whatever.
Anyway, I never figured out how to leave. I just did it the moment I realized I could not spend another minute under the same roof living that lie. At that point, I couldn't stand to NOT leave. I don't know what allowed me to let go of the shreds of hope and denial that had kept me there so long. Maybe the tipping point just comes when it comes. Working on yourself helps.