my dear frined, your ex is a fu*king cu^t
the problem is not your son who is being manipulated by this piece of fecal matter.
don't take it out on your son. Remind him at appropriate moments that he needs to call YOU dad. whatever he calls the other guy is not important, really, because that poor shmuck is also being manipulated...
you son should call you dad. period. don't yell at him or get mad, just make a reminder when you have to.
be unemotional about it like you are reminding him to call a tree and "Tree" or the sky, "Sky". Like you are just teaching him the correct names for things.
and I like the idea of calling your ex by her name rather than "mommy".
but never say anything negative about your ex in front of your son. THAT is a diservice to him. I'm sure you know this because you are not a horrible person like she is.
Just remember that she is trying to push your buttons. Don't give her that power
