I am following your sitch right along because last week something did shift in my H and he moved into a different "age" similar to where your H is now. He now updates me on house stuff too! So weird. I am reading all the advice you get!
Personally, I have gone with the strategy of trying hard to pattern the behavior I want to see him pattern toward me. (I think this was one of the things you also considered doing, too.)
So, with zero expectations (I think of H as house guest, not H) I invite him nonchalantly. I just say: we're going to x, if you want to come feel free to join along. I mention whatever it is (whether it's this afternoon or something in two weeks) as I am on my way out the door. I kind of don't "wait" on his answer as I noticed early on this seemed to be too much pressure for him and he waffled. I kind of do it "in passing" but very politely. Like I would invite a house guest. If it's something that requires him to answer, I just say "if you want to come let me know so I can buy you a ticket."
Me 41, H 47, M 15 yrs, S11, S13 BD 1: 11/4/14 we work on it; really I pretzel myself BD 2: 3/31/15 H goes down to "dorm room" 8/15: H back to MBR 10/15: H back in dorm room 1/18: H files, now divorced
