A.,
I am so sorry to here about your marriage. I have gone through the exact same thing regarding sex and falling out of love. I too have been to the point of leaving. Before I did, I decided to give him one last chance and depending on what he said was the deciding factor. I told him that I had something serious that I wanted to talk to him about but wanted to wait until the kids were in bed so I was not interupted. That gave him a bit of time to think about what I needed to say. Once we started to talk I told him that I am not happy in our marriage and I need help coping. I told him that I wanted both of us to go to marriage counseling. When he asked for my reasoning, I put it all in the "I need" format trying not to accuse him. (I need physical touch and need to hear positive things) He knew that I was really serious because I only ask for marriage counseling when I am at my witts end. He appologized, said that he would try harder to meet my needs and he actually stuck to it. (read the book The Five Love Languages - it explains exactly how to love your spouse in the way THEY (YOU) need to be loved. It makes it easier for you and the other person to understand what you need in a love relationship- easy reading) granted, it was only a month ago and now he is gone for 4 months working, but when he calls and we e mail, things are better. I am wondering how it will all work out when he gets home. I have not let my guard down yet. One reason I think it is so important to stay together is because I have also a child from a previous relationship and we have 2 together. I do not want another nasty divorse to deal with for the rest of my life and I want the kids to know that no matter how hard relationships get, you need to try your best to work them out.
Now, when it comes to the stealing money and using it for drugs, that is where he needs help. If he is still using or selling tell him that needs to stop - no acceptions. Offer to help him find help and that you will support him. Drugs and alcohol change personalities and you want the old hubby that you married not the druged hubby.
I don't know if any of this will help, but it has helped me. Even though my husband is not home, I am still seeking help for myself. I have started see a psyciatrist to help me deal with all these issues. If you want your marriage to work, take the steps to help yourself first then help him.