Oh wow
You are all living together in the same home? I'm glad you found the site. These divorces are hard enough without inlaws living under the same roof.
Do you suspect your ex's parents may have some BPD pathology of their own?
What stage of the custody process are you at, and what are your thoughts thus far about your lawyer?
If you haven't read it already, William (Bill) Eddy's book Splitting: Protecting Yourself While Divorcing a BPD/NPD Spouse is a must-read.
Has your ex made any false allegations so far? What is your relationship like with your child?
Apologies for pelting you with so many questions

LnL