NoDirection, I really do understand what you are saying, your sitch sounds to be mirroring mine. She told me the same thing she was only with me for the kids, but also would say I ought to just leave and you can have the kids.
She was living the same double life, acting like everything is fine between us, when the kids were around, all the while starting to alienate us all.
The truth is my W and it sounds like yours as well, are searching for something they thinks they want, and that is anything but what she has with you. Sad fact is that while in that frame of mind they are really being selfish to what is best for the children, and that is having both parents. In this ignorant society with so many so called experts saying that children are much more resourceful then we give them credit for, D is so acceptable, to me that is a load of garbage. Children need to feel that they are secure, and that both parents love them equally. When one parent acts so selfishly, they will see it, and blame that parent, this doesn't mean that they don't love the parent, but their relationship will be forever tarnished.
I speak from experience on that one, I am a child of D, and for so long I blamed my dad for all of it, because in my eyes he was the one that was being selfish, he wanted someone other than my mom and our family. It was only through my C, that I have been able to forgive him, and start to form a new relationship with him. I never wanted my kids to feel like that, but it seems like the lines have already been drawn especially between my DD11 and wife. I know that your son is young, but it can happen, later in life.
Until she is ready to open her eyes, be a real mother to your son she will not see all the harm she is doing.
You have to do what is best for your child, it sounds like you are the only one who is, at this point, I commend you for it. Continue to build that relationship with your son, let your W do whatever, now that I think about it, I apologize, I think it would be best not to have any kind of R talk with her, no talking about how things are good/ how things are bad, at this point, it will be useless. Take time to calm down, I don't mean like tomorrow or the next day, I mean take a lot of time, don't approach her in anyway, let her come to you, openly and sincerely. And still I would avoid all R talk, until you talk with a C, or a DB'ing coach.
Meanwhile, take this time to work on you, I know it is hard, but you need to detach, take the focus off of her, and saving the M, put the focus on you, do what you can do for you. I don't know if I gave you the detaching link, but if I did, go back and read it, and then read it again and again, it will help. let me know if you don't have it, I will find it, and give it to you.
You are strong, stay in the Lord, you are in my prayers, Take care.