Fake it until you make it right?

My husband and I have been together for 17 years married for 13. To outsiders we appear to have the perfect life. Healthy kids (20 15 3), great careers, financially stable, nice home, get along great etc etc etc. What people don't know is that my husband is a former drug addict. Not just an occasional recreational use but a full blown, spend 2-3k a week went to rehab addict. It nearly destroyed our relationship years ago. I drew a line in the sand and he said he would get clean. He didn't. I threw him out in 2013. He totaled my brand new truck two months later, I found it I was pregnant, he lost his job and I let him move back in. I made it clear that I was not interested in being together and that he was just staying here until he healed (very serious injuries). I told him I was going to raise the baby on my own (I am very independent financially. He was on the road to recovery (and using the whole time) when he had a heart attack. I performed CPR and he survived. He spent over a month in a coma and had months of recovery. I decided to stay and try to work things out. He did great. He has been the husband and father I dreamed of. Life was pretty near perfect. Except I can't let it go. I cannot forget all the terrible things he has done to me/said to me over the years. Sometimes I look at him and question why I saved him. I think I should have just let him die and I wouldn't be going through all this right now. Last Christmas he relapsed and overdosed. He had my kids with him, and they could have been hurt or worse killed. I told him that was it. It was over. I wanted him out of my life. He found an apartment but never left!!! He refuses to leave. He thinks everything is fine because for the past year I have been faking it until I make it. I have some financial things that I have to get sorted before I can just walk out. Until may I was disillusioned that he was leaving. I now realize that he will NEVER leave. He will NEVER let me leave. He is verbally abusive and very scary when I have tried to leave. I am also devastated of what this is going to do to our youngest child. She adores him. And he adores her. I cannot imagine them not being together every day. The guilt I feel every moment eats away at me. I don't love him like a wife should love her husband. I only see the person who has caused me extreme pain when I look at him: I don't know how to tell him I am leaving without him hurting me or himself. I have been faking it for so long I don't know what to do. We have tried counseling, it does not work as he is in complete denial. To complicate matters further while we were separated I was seeing someone else. I have never been intimate with this person and we have kept things strictly platonic. He and I dated before I met my husband. I ended things as I was a stupid young girl who wanted a "bad boy". He is amazing. I was head over heels in love with him then, have always had a warm spot for him in my heart, and am pretty sure I am still in love with him now. Even if I never saw him again I would be in love with him. In my heart I have always wanted him but the timing has never been right. He in no way pressures me or even tries to make me leave my husband. He was not involved in my life in any way until just recently. I would often ask about him from old friends or drive by his parents house when I went home. Never ever stopped or attempted to contact him until things got bad here. Saying to never see this man again is fine. But I can go months (or twenty years) without seeing him and think of him almost daily.