Daisy -
My husband is a recovering crack addict, and although we spent some time separated, we are still married and living together. I like to think I am now supportive without being co-dependent, but that wasn't always the case. I had to learn a lot about what co-dependency was, how I was enabling him, and what I was getting out of our (at the time) crappy relationship by sticking around. And I had to learn how to detach from his addiction - I'm still learning that part.
If you think you are being supportive, that he is on a real road to recovery and that things are looking up, then what does it matter what strangers on the internet think? I'm curious to know what your real question is, because I don't think it was the yes-or-no question you posed at the end. If you're asking if people do recover, and if marriages can withstand addiction with recovery, then yes, it is possible, but it isn't easy.
Snorting heroin isn't like having a couple of Twinkies on the sly. I suspect that your husband has done some things that he isn't proud of, things that may or may not come to light as time goes on. Perhaps there are things about his addiction that you don't know yet. More will be revealed, and only you can determine what is acceptable to you. I hope you never have to know how lousy it feels to be hopeless. Good luck.