Peaches -
You have every right to be hopeful. You just have to place your hope in yourself rather than someone else. You can be happy - no matter what he chooses to do.
You say that he crossed your boundary. The thing about boundaries is this: They have to have a consequence. Otherwise, they're not boundaries. You can't rely on him to respect a boundary just because you've set it.
An example would be, if you don't call and make a counselor appointment by Monday, I'll make one for myself and go without you. You don't have to remind him or nag him about it. If he doesn't do it, you follow through on what you've already decided you want to do.
My H was surprised when I actually started doing what I said I was going to do.
If you're not ready to set a consequence for his using, don't go there yet. Baby steps.
Hugs - L