If I could transport you into my mind when I was going through MLC you would get an idea.
This is my opinion of your question about your wife losing custody.
If you asked her if she loved your son.....her answer would be yes, of course, but not many or none of her actions would match. It's as if she is thinking along one time period but living in another at the same time.
Describing MLC is tough because the mind is scrambled. Why does this happen....I don't know. All I can say is it does.
The common sense person looks at the actions and thinks WTF. It absolutely makes no sense.
You are going to keep beating your head against a wall if you try to figure this out. Just keep being the rock in your sons life. I know this may sound trite....but your where your supposed to be and your life will unfold before you as it should. This life is a journey(interesting) but we live in the present moment and that is where we are supposed to be.....not in someone else's mind but in our own moment, that allows us to make the best decisions that we can.
Keep living life for you and your son. At the moment that is what you have and it is important.