Morethan2's story is so important! It shows that we can't really know what's in our AC's minds or what the dynamics of their marriages are. I know it must be terribly hard to see DS criticized and micromanaged this way, aquafish. But, unless he says something, you really don't know how he feels about it. He might even find it a relief after his challenging job or think it means DIL is a really caring mother.
If he doesn't like the way she's treating him, I'm sure, after a while, he'll take it up with her. No matter how much it bothers you (and it would bother me, too), as others have indicated, it's not your place to fight this battle for him. Your getting in the middle would only make it worse, I promise you.
Glad things are looking up and that you plan to take the advice you got here. Hope you had a great Christmas and that things get even better in the New Year!