I'm going to come at this from the 'alkie side' being one myself, rofl.
If he continues to work his recovery and reaches his 4th step, he will probably be asking a lot of folks what he did. I know I had to, and many years later still have 'gaps' in my past life.
Until asked, I wouldn't say much. He is attempting to 'digest' and awful lot of information right now and hopefully put some of that information into action.
I'm more concerned about YOU. What are your motives, so to speak in being 'his friend'? Check your own motives and the answers will come.
I only ask, because by checking your own motives now, you may be saving yourself great heartache and pain.
I would hope that should he reach his 9th step and come to you to make amends, he will already have spoken with you on his fourth, so that he knows what he is making amends for. It is your right to ask him what he is making amends for and if he does not know all of it, then fill him in on the 'gaps'.
My personal opinion is if and when he asks, tell him.
Please keep posting and let us know how YOU are doing, we do care very much.
Love and hugs,