Takes two to Tango, WAW. He's as much at fault as you are. Your in-laws sound like very lovely and kind people as well. Don't stay in a marriage for your D or your family. My mom did that for my youngest, it's made her slightly bitter and she's been unhappy for years. To the outside world, she 'had it all.' Except her H was/is an utter self-centered [censored].
You are willing to work on your M. Your H isn't at the moment. I hope the signs of change you're seeing are real and that you can move back home in the future. Hang in there. I'm not going to say it's not your fault, but it sure as hell isn't ALL your fault.
Regarding your H's age. I'm 36 and still like to get out and go places. I think that's personality more than age. Though you may be on to something with the older/younger control dynamic. Of course, GD and his W are the same age and there were still control issues. Regardless of the cause, you've identified the problem at least. Keep focused on that until you're back together, then you can get into the cause of it if you want.
BD
My latest
Me: 36 W: 35 2 D: 9 and 5 T: 16 years M: 12 10/4/06: Bomb 10/5/06: Ended A 4/22/07: ILYBNILWY