I am new here, but have been part of a divorce forum for years and your problem sounds like the ones posted over there.
First, you stay away from him by going NO Contact. No phone calls, no emails, no Facebook likes, in fact, delete him from any social networking sites you have.
Second, You will feel horrible for a while. I know when I left my narcissistic, cheating ex, I questioned myself over and over. I knew in my head it was the right thing to do, but my heart was another matter. Your head is right, listen to it.
Write down everything that frustrates you, drives you crazy, all the stuff you "put up with." When the going gets tough, read the list. It will give you the strength you need to get through this.
When I walked in on my ex's affair, I felt dead inside and in reality, I was. What I did not know was that was also the day my life started over and I am so much better off now. My thoughts are my own. I don't have to check in with his mood 30 times a day. I have MY life back.
This will be tough, but in the end, you will better. Stay strong.