Of course you're confused, so is he. Very confused. You cannot figure this out and guess what? Even if you could somehow pinpoint the day and time of his childhood experience that MADE him do this or that, it would accomplish nothing. You can't change his past or what he's feeling/thinking no matter how well you articulate. I'm an attorney and if arguments worked, or if our M had been a case, I'd have won at the Supreme Court. But logical arguments and fairness and justice have so little to do with this.
You must let go of what you have no control over--it's a costly illusion to think you can fix this or control it, and it's a waste of your life, which is shorter than you realize. You are only in charge of your life, and that's only if YOU are taking charge of it. Remember about thinking of your life as a novel. Who is writing yours? How's this chapter going and what will happen in the rest of your "book"? Be the author of your life's book. Make it go YOUR WAY, not someone else's, let alone a confused person who isn't in charge of their own life.
Keep up the DBing, b/c as far as I can tell, you've been getting results. Nothing is worse, and things are semi-stable as far as conflict free time together. Warm memories, etc. to counter the negatives, good. I think that your d1 leaving for 6 months would be hard no matter what, and you will miss her. But that's life with growing children and we must remind ourselves that the alternative, i.e., them living in our attics waiting to "find their bliss" is really much worse...
But then, you wanted to see what the calmness was like, so try to experience that and enjoy it while it lasts. More later, stay strong. j-
M: 57 H: 60 M: 35 yrs S30,D28,D19 H off to Alaska 2006 Recon 7/07- 8/08 *2016* X = "ALASKA 2.0" GROUND HOG DAY I File D 10/16 OW DIV 2/26/2018 X marries OW 5/2016