Blackandblue, with regards to you contributing to his relapse, I am sure in basic terms you are right. However, what you have to realise, is that if you didn't break up with him, something else would have happened to trigger a relapse. Life will always hand you lemons in amongst the honey. An addict serious about recovery will stay clean even during the hard times.
I remember I stopped smoking for about 3 months when I got the news that my brother committed suicide. I was in an absolute state and the thought "I need a cigarette" crossed my mind. I also remember the next thought was "a cigarette won't fix this, nothing will" and I didn't start smoking again because I was done with smoking.