Good for you that you recognize that you need to take care of you. It's not easy to make the decision to leave... seems like it should be, given the circumstances, I know. BUT... you didn't fail. You didn't cause the problem and you deserve to have your life and to be happy.
I made the decision to end my marriage too. Once I told my AH, it took 6 months for him to move out. He has been out for only a couple weeks. It has been very hard. I don't miss him... not one bit... BUT, we have two kids and I am having trouble getting used to that fact that my life is now my own. Not sure what to do with myself, but know that I love the peace and not having to deal with the issues that his drug use caused. Would love to tell you that I am happy, but not yet. Working towards peace, but I know I made the right decision even though I have had to do the hard stuff to make it happen.
HUGS to you!