Glam, You have to understand that it's not that he doesn't care, he just doesn't have it in him right now to show any type of emotion, etc. He's in the world of depression. Have you watched the commercials on tv for Cymbalta? The depressed people sit around, do nothing and stare at the walls. They have little or no energy and when they do get up and do things, they are very, very tired and it's an effort to even pick up a spoon. They have no interest in anything around them. Depression hurts not only the person experiencing it, but everyone, including pets that are around them.
Him turning 40 didn't help him feel any better. I can remember when my xh turned 40 and did that date and age do a number on his head. They look at 40 as over the hill and they are old, youth is gone, etc.
I know you are feed up with his behavior, but there's nothing you can do for him. Just let him go, leave him alone and he will eventually touch base w/you again. It sounds like your "expectations" were up again....Glam, knock them down to zero for that is all he has to give now...nada.
Focus on you and your children. You need to continue moving forward and if he shows up or calls, fine, if he doesn't...go on w/your plans. Do not plan your day around him, for he's a very lost camper right now.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.