The problem here is that you are always going to feel/think differently to his mother, he's her child, always protective (it reflects on her too) of the 'lie'
Whatever he says to anyone is only framed in the way that he can make it work for his problem and those enabling him.
The problem I've found with the way the brain works is that this whole 'rescuer mentality' is actually harmful to us codependents. Discussing the problem should be restricted to lawyers, professional therapists etc
Any grapevine hearsay always has a vested interest in something other than the truth, it is designed to be slanted to show the messengerinthebestlight.
My thoughts here are that yes, you are kidding yourself....
Get off the crazy-making bus, extract yourself from ANY and ALL interactions that stray towards gossip or how things 'should' or 'ought' to be/turn out as far as your ex is concerned.
Stay true to youxx