I applaud your commitment to getting the truth. I think that as others have said, that's impossible the way he is behaving at present. Again, it is not your responsibility to get the, it is his to give it. What would be a positive sign is if he came to you and said, this may mean you never want to see me again but here is the timeline and details of what happened, complete with evidence if requested (there is always evidence, people don't fall in love and destroy keepsakes) and here is why I think I allowed this and why I would be different in the future. And for you to be satisfied with this.
I actually am one of the few people who will occasionally encourage communication with the OW, because sometimes that just gets the bubble burst quicker and sometimes yields facts which hurry things along and stop people's lives being wasted. The one piece of advice I can offer is this, do NOT do this in conjunction with him, any communication like that must come out of the blue, to her and him, because I'm afraid otherwise they will get their stories straight, no matter what the state of their relationship. It is as useless as the newly clean phone he offered you. This fact has always bothered me, not just because of what it shows about his former lies but also the lack of respect for you that he would even bother. It's like he thought you were thick.
No man wants his secrets uncovered no woman wants to be portrayed as homewrecker. As I said, observing a call on speaker from him to her with no time to prepare is often good. Or being in touch with her alone. Honestly? I once received a call from a man I cheated with telling me his wife would phone and begging me to lie. She didn't but I would have, I was young and stupid and didn't want to see him again and also didn't want to be responsible for a marriage ending. More tellingly and horribly, he still, years later contacts me occasionally to say he misses me and wants to meet up. I also know he cheated multiple times with others. I obviously ignore. I feel very sorry for his wife and I deeply regret everything about that. I would hate for you to be in the same position.
I think one of the most impossible things about an affair uncovered is that short-term it always seem easiest to stay, the enormity of splitting a family etc is too much to bear. But long-term there is no doubt it is the tougher route. However, since we always live in the short-term (it is always 'now') most people choose to stay and some are destroyed by it for years (long-term). I have seen great marriages come out of such situations and be repaired (see JonestheSteam on here for an example online) but never in the way you are describing. What you are describing is becoming so strong and independent that it would be impossible for you to be hurt by him in the same way again, which isn't the same as building a new marriage, which is what is required and involves change in behaviour and character from him, not you.
To explain further, 'detachment' is a state in which the subconscious expectation that it is inevitable to get back together is gone, leaving the betrayed truly free to choose their path in life, as if both are equally appealing for different reasons, and to securely and maturely choose the one they see clearly and really want, rather than acting out of fear/expectation/'the children' and denial.