Have you considered trying Alanon or Naranon...maybe while he is working his program or enjoying his me time? I suggest that especially since you said you really can't talk about your relationship with others since they wouldn't get it. Folks in the anon programs definitely get it and the face to face support is great.
I understand your concerns and I particular understand how you feel about the lies...unfortunately there is no magic crystal ball to show who stays in recovery and who doesn't The fact that he jumped back into his program pretty quickly sure sounds positive. It certainly is easier not to have the fear of relapse in one's life but at the same time, it's been my experience that many of the addicts in recovery I've been privileged to know are some of the most caring, insightful folks going. They have been to hell and back and have found a better way to live.
You sound like you are thinking with your head as well as your heart and that's a good thing. Keep reaching out.