Drop the rope, take the pressure off of him. He can't tell you why things happened the way they did because he doesn't truly know himself at this time. In time, he may better understand the whys, buts, ifs, etc., but right now, he's still confused and the only way he sees getting any relief is possible a divorce. Unfortunately, that won't help him either because the conflict is within himself and until he can resolve those issues, they will haunt him for a long time.
The best thing you can do is live your life to the fullest and just leave him be. If he calls, you can decide to either take the call then or wait a bit and return the call. Don't be too quick and responding because you are going to be living your life for YOU.
When he comes over to discuss the financials, keep it on the financials and if he talks to you about other things, listen and if you truly listen, you'll learn more about where he's at now. If he asks for your opinion, give it, but otherwise just nod and listen. Don't bring up the relationship on that ow you call Bubbles. She's all that right now...Bubbles because one day, her bubble will pop and he may very well realize what he's gotten himself into...but he needs to figure that out for himself.
You've got this. Leave him and Bubbles floating in the air.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
