You do not give any info about the situation. If the "clever abusive woman that lives with his dad" is the dads girlfriend/companion and you are divorced from your adult son's father you have no skin in the game so to speak. So really you have no say in this. If the "clever abusive woman that lives with his dad" is your ADULT son's girlfriend /companion and the girl is residing with them then again you have no skin in the game and your son is an adult so you really have no say.
If you want to paint a clearer picture that might help.
If the "clever abusive woman that lives with his dad" is the dads girlfriend/companion and you are divorced from your adult son's father you have no skin in the game so to speak. So really you have no say in this.
If the "clever abusive woman that lives with his dad" is your ADULT son's girlfriend /companion and the girl is residing with them then again you have no skin in the game and your son is an adult so you really have no say.
If you want to paint a clearer picture that might help.