John, she's just using the same tactics she has in the past to manipulate you AND your son. Using your son the way she did was disgusting and cruel.
Please, think carefully before you commit to any MC with this woman. She doesn't appear to be properly motivated. I know you pursued (sigh), you said some things that told her she had your balls in her purse, right before the mediation started.
I wouldn't trust her as far as I could throw her. Her motivations are to get you to agree to 60/40 (why I don't know, it's not that diff than 50-50) and more alimony. She'll string you along, and then she's going to jerk you around again.
Was the mediation binding in any way? Did you sign any agreement, or are you going back for more?