Just want to point out another thing.
I tried to talk to her, explain he is just upset, she wont listen.
This sounds like you are focusing more on her than your son.
If your son over heard that conversation it would sounds to him like you are taking her side and NOT your sons.

Now that is something that you can never let happen.
That could quickly move your son out of your end of the ring and in to hers.
Be there, validate and listen.
His rock. His safe place.

Me: 34
Stbxw: 30
D:5 D:3
Mini bd: May/June 2019
Married: Aug 2019
BD: 6th Dec 2019
OM Confirmed: Feb 2020
March 2020: I filed for D
Waiting for D to be finalized and W to move out end of January 2021