Hi there, I've had my fair share of experience as a co-dependent. I'm now struggling with my own problem with alcohol. So when I dated a crystal meth addict I tried to save him for 4 years. I didn't know what to do. All the controlling, ultimatums and anger and love didn't work. Thankfully I found Naranon the equivalent of Alanon and the nature of this forum for family and friends.
To make a long story short I highly recommend you pick up "Co-Dependent No More". It's how to deal with someone that has an issue and to maintain your sanity and possibly save your relationship.
A few things it taught me,
Detach with Love
Let Go and Let God (or whoever you choose, just let Go)
When my reactions to his actions changed he changed. It was insane. I just stopped participating in the madness. I didn't leave him, and he detoxed himself on his own and stopped doing the drugs. We went on to have a happy relationship for a good year, and then his demons returned. Well I was done at that point. Only you will know when you are done.