I can think of a couple of things.
You mentioned that your dog gets plenty of exercise. May I ask how much you think is "plenty"? I have found that people have widely different viewpoints on what is "plenty" of exercise.
Whatever the level of exercise, I suggest you double or triple it for a couple of days. If he likes fetch, keep throwing until his tongue is hanging--being careful not to overheat him or cause injury. Wear him out really, really well. See if he sleeps better after been completely and totally exhausted.
Also, is it possible he is getting rewarded for the noise he is making in the crate? Even negative attention like scolding can be rewarding enough for the dog to keep on doing it. I suggest covering the crate with a blanket, totally ignoring the barking and only letting him out when he is calm and quiet.
Best of luck and hope all of you can sleep better soon,
Linus van Pelt Haus Juris. My Sweet Babboo, born March 17, 2014.
Madeline Ronan Heart (Maddie) Dec 1997 -- November 22, 2013 Rescue GSD, Sable