Welcome to SR, but I am sorry for the reasons that brought you here.
Putting off the wedding sounds like the best plan. You and your love are no match for addiction. Its not personal, but an active addicts first love will always be their drug. Look at how low he sunk to get his drugs!!! And that's not nearly as low as he can/will go.
To answer your question about things turning out good again, sadly, less then 10% recover for life.
I had too learn that my love wasn't enough, my addict wasn't special and my marriage wasn't special enough to beat it. Addiction does not discriminate.