Treese, I'm not trying to pound anything into your head, but I'm trying to get you to think before you vent at your h. Just as he is in MLC and is looking at you as the problem, etc., you are doing the same to him, i.e., looking at him as the problem for all of the problems happening in your life. We can only take ownership of our own lives and the mistakes we have made.
As for the mil, I'm sorry she did what she did, but your h wasn't at fault for that. He has no control over her anymore than her husband or you would have. As for your son saying it's a secret, he may have come up w/that on his own after the way that you responded to his gift. I do not think your mil is punishing your daughter at all. Older folks have a different way of looking at things, i.e., they give to the children who are under a certain age and since your daughter is 23 and living on her own, they may have felt she didn't need a monetary present. I know that my own grandparents were this way. Yes, it hurts, but you cannot change the way that they look at things. Two wrongs will not make a right. I hope that your daughter will invite them to the wedding just to show them that she's above such things.
One of the lessons that I had to learn was to not always taking the behavior of others as punishing me. I had to learn to not think like a victim and feel like everyone was out to get me. This is something all lbs need to learn....you will too.
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.