Problems Settling Down to Sleep

My husband is the ADHD one in our marriage.  I've been close to "done" many times, but I also took vows and we continue with our mantra that "divorce is not an option."  Married for almost 21 years, together for 26+.  Two teenagers, a dog, and two cats.  He was diagnosed in 2004.

Biggest problem *right now* is getting him on anything closely resembling a functional sleeping pattern.  He stays up late (wee hours), gets up early to deliver kid(s) to school, comes back home, has a large breakfast, and then goes back to bed for several hours.  He then picks up kids from school, and once they're home he's distracted with their needs, trying to get himself focused on something, and the next thing ya know it's time for dinner, a little evening TV, and then we do it all over again.  He says he can't settle his mind down until the rest of us go to bed and leave him alone.  Then he either watches TV or plays cards on the computer for two or more hours until he feels his brain slowing down.  I've read, and we've discussed, the fact that screen time is super-stimulating to the ADHD brain, but he continues to do it.  If one of the kids gets up and has a question or needs something, he becomes absolutely incensed (a common response to even the littlest things). His "winding down" clock starts all over and it's another hour or so before he decides he's ready to go to bed.  The he does some sudoku puzzles once he's in bed, so he can wind down some more.  This vicious cycle leaves him depleted and unable to accomplish much of anything.  Obviously he does not work outside the home.  That's a story for another time.

So, my question is if it's legitimately possible for an ADHD brain to take 2 hours to settle down enough to sleep?  Are there any proven techniques to help him be able to calm down in 15-30 minutes instead of two hours?  Am I being completely snowed here and he's just letting his ADHD run him?

Any thoughts or suggestions are greatly appreciated!