Because she did something "physical" to your son, I would really watch that. You should speak up and put your foot down if it happens again. I called my W out about her anger and told her that she needed to deal with her own issues and not take her frustrations out on our Ds. Her face literally drained and she said she didn't realize what she was doing.
Sometimes they need that "slap of reality".
Your sons didn't choose this. She did. She has to deal with what she's doing and not take it out on you or them anymore.
In terms of your ILs sitch, I'm not surprised she sees you in a hostile light based on her experience.
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.