Tell your MIL that as much as you'd like to, you can't because of the reasons you specified. Reiterate the fact that you love and miss your son very much and would like to reconcile with your W, but she's got alot of junk to go through personally.
If you move and it doesn't "snap" her out of her funk, you will be left with nothing. That's not a good example for your son.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.