It sounds quite clear his mother is on YOUR marriage's side, so him complaining to you and her isn't goign anywhere.. he's just trying to SAVE FACE if you understand that...
He has been publically humiliated, but he brought it on himself... any challenge he throws at you is just his OWN embarassment and him wrestling with how to DEAL with that.
WHy would you lower youself into that kind of argument. IT's STUPID.
LET HIM STEW for a few days on the MESS HE MADE and YOu just EXPOSED.
Let him squirm for a few days, this is how you grow up... do NOT cater to an argument.. its NOT likely gonig to HELP you right now..he's "seething with entitlement" still.
He needs to COOL OFF, but his instincts are driving him to confront people and FIGHT... just stay AWAY from him until he has more control over himself.