Keep reading and learning about codependency. I had so many misconceptions about what it was and wasn't.
Enabling is doing for someone what they can do for themselves. Do what's necessary for YOUR peace and well-being (around the house, etc.) and let him manage his own needs. He may not change a thing, but he'll get the message that you're not his keeper.
Are you attending Al-Anon? There is no feeling of shame when you share with people who have been there. For me, it was it was a huge relief to be with people who got it. It was like a weight had been lifted when I knew I could just put it all out there in a confidential, non-judgmental environment.
And the sex? Well, if there is nothing in it for you, why bother?
Leaving my ex was pure hell. He was the love of my life and it was torture. It took me a few times, but when I finally left for good, it was because I was entirely spent. I couldn't do it even one more day. And I have built a beautiful new life for myself.
Leaving takes courage. If it's the choice you make, it will happen when you're ready. Keep reading, keep posting, keep asking questions. Focus on you.