BB,
You need to move on. Your bf is not in recovery, he's in denial. 3 years of history, no matter what the emotional ties you have to them, are not reason to subject your children to this. I'm sorry if that sounds harsh, but I've been there... I've been sober for a year and a half but while I was drinking and using, when push came to shove NOTHING got in the way of my habits. It's not about you, it's his addiction and it will continue until he has come to the conclusion that he can't use or he will die. Sounds to me like he's not even in the same time zone as that level of self-awareness.
Cut ties and move on. Life is really short, BB, and this relationship is a waste of your time and love.