Wow. There's a lot going on here. I'm going to leave the legal angle to others who have more experience with that.
You're way inside his head right now, ascribing all kinds of thoughts and motivations to him that might not actually exist. You'e positive that this is "the bottom he needed" and that you helped to bring it about. You're equally positive that if he finds out about your role in the DUI (which really might have happened anyway, given how out of control the whole situation sounded) that "he will go off the deep end, relapse and most likely try to die."
That would obviously be counter productive to what I was going for by turning him in. I'm just really worried about him finding out because he is FINALLY turning things around and I don't want this to screw that up. Not sure what to do though...
This is you trying to control an uncontrollable situation and then trying to control another person's reaction to that situation. What I wish I had done when I was wasting my precious energy trying to orchestrate my ex's bottom and control reality so that he would get sober is to focus that energy on myself and my children instead. Your bf is in good hands right now getting professional legal and psychiatric help. Maybe what you need to do is take your hands off. Totally foreign concept, I know, lol. How will anything get DONE unless you take care of it, right? Believe me, I know the feeling. But maybe it's time to let him start learning to handle life on life's terms.
It sounds like things have been out of control for quite awhile. Are you in Alanon or any type of therapy? I had it in my head that if my ex got sober, my life would be just about perfect. As a result, I neglected myself and my children due to my obsession with fixing him.