First why would you want to be with someone that doesn't want you. I mean I know you love him but if he doesn't reciprocate then you are setting yourself up for so much more like affairs etc. Take care of yourself first and then show him why he should be with you not tell him. Sit down and talk to him about it and honor his wishes. It will be hard to accept but trust me it would be better in the long run then corner someone into staying into a relationship. If he goes to get divorce or annulment or even a legal separation don't stop him express your desires and ask him to give you a chance if he does then great if not then it wasn't meant to be at this particular time. Get right and then if it works out later then it was all meant to be. Mainly you need to get healthy first before any relationship to work. They are hard enough as it is.
You need to get better for yourself and nobody else the rest will be what will be if he doesn't want to stay there is little you can do to change his mind ,but if the threat was in relation to the drugs issue then can you blame him for threatening this kind of action if you don't want to loose your marriage you need to try harder and not just about the drugs make changes today tell him how you feel honestly good luck