So glad that you had the courage to come here. I hope you realize that the majority here are LBS and whenever they read a story such as yours they naturally want to lash out. Truth be known, even some WAS might let you have it, also. But I hope you will stay here until you get the advice you need in order for you to be able to clean up your life and do what's best for your W and children.
It's so tragic that we don't really see what a treasure we have until it leaves us. I think that might be the case with you. Would you say that you took your W for granted? She must have really trusted you for you to get by for so long before she found out about you & OW. Would you say that when your W actually left you that that is when you knew you wanted "her" above anyone or anything else?
You may get frustrated with questions that will come your way, but it helps us to understand your stitch better.
Tell us how you have been dealing with the separation. Have you been pursuing your W, trying to talk her into going back to you? Based on the information so far, my thinking is that you need to back away from your W. Don't put any pressure on her at all. Do the two of you have a visitation set up for your child? If you don't, then you need to come to an agreement about that. Then you need not to contact her unless it is concerning him. Everytime you contact her that puts pressure on her.
It will be hard, and scary, for you to leave her alone, but she will need "time" to prove that you are not involved with the OW. Also the OW needs to know that you do not want her (OW) when you are not in a R. She gets her jollies by knowing she is controling your life so she must find out the truth.....that you would not have her even if you were not married!
It may take a divorce for both women to decide that you do not want the OW and that you truly want your family together. Your W is very hurt and terrible vulnerable now, so she may go through with the D, but people have gotten together after a D. Has she filed yet?
Is the OW still going around your W? If she is, I'd be concerned about that. Makes me think of "Fatal Attraction".
Whatever you do....DO NOT contact the OW. Break all communication with her once and for all.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!