Prior to BD I withdrew and went silent. Do you see this as a problem or do you believe that she has seen the changes? MWD seems to suggest not going dark/dim if this is an issue and I believe it is!"
You are in a new position now. You showed her your changes, before she left but she still chose to leave and not work on the R. From this point on, you must look at it with that mindset.
"What do I answer if she ask: Why don’t you call back? Why don’t you want to talk? Why don’t you accept my invitations?….and likewise. I see this coming and would like to be prepared! Should I just go with: Well, I don’t feel like doing it and if she ask why just back off immediately and tell her that this is just how I feel."
Don't make up excuses. Don't tell her you don't feel like it. You aim this at her choice. This is the result of her choices. Simlply tell her that she chose to leave the R and along with her leaving...came a different R for the two of you. She should have realized things would be different. If she continues to ask about it, then tell her that You will continue to co-parent but you will not be available for a buddy-buddy R with her. You will be friendly, but she rejected the R she had with you, so why should you want to be her BFF?
Don't fear her getting mad, b/c she probably will, but when you do tell her this...you pick up the reigns to what you want in a future R with her. Understand? She won't like it and may spew, but that is okay. You don't have to stand there and listen.
The point is to shift gears so she can get to the place that she misses you as a H and lover. She can make friends with anyone, but if you try to be her BFF you will be in limbo with her forever. Just don't get into that trap.
"I also believe she will involve others when I go dark/dim and that I might get the same questions from her family or mutual friends. How should I handle myself and how should I answer if this happens?"
That is another trap. Don't discuss it with anyone. If you must give an answer, simply say, "She made the choice to leave me, not the other way around. Now I move forward.". Then end the conversation right there. Refuse to listen or answer any more. She may try to have someone to intervene for her, but don't play that game.
"What should I do about FB. I don’t use FB more than once or twice a month but should I defriend her and if so what about her family and mutual friends?"
Defriend her! Be prepared for her not to like it, but so what? This is part of the plan. It hits her up beside the head that you don't have any interest to be a buddy of hers. You wanted a R that was set apart from friendship. You won't settle for being her buddy. (This is what I'm telling you. ). But if she asks, just reply with, "What did you expect after you left?". Just don't get into a conversation (which you tend to want to do.)
"How should I handle myself around XW1 – please read my previous post about her acting’s. "
I don't think you need to get chummy with her either. You are still vulnerable to a point, and it seems she is taking advantage of it. I think you need to be very, very careful of XW1.....if you want to R with your present W. I don't trust a females who do what she's doing.
I would turn down invitations that included either of your XW's with their children. You can tell XW1 that you need to not be involved in family-style togetherness for a good while. You don't have to give her a reason. You do need time, and you sure don't need an XW confusing issues for you.
I think you need to stay away from your present W's relatives for a while. It helps keep down confusion, confronting nosy questions, etc.
Make your own plans for the kids to have their birthday parties with at your house without the W. She can have them a party at her place. These are some of those hard bridges to cross, but it will hit her with the reality of her choice to breakup the family. Same at Christmastime. Very hard to think about right now, and don't bring it up to her, but just know that you will need to deal with it. No more shared family events with her. No more shared time with the kids. This needs to hit her right between the eyes.
The goal is not about upsetting her, or making yourself look mean. The goal is to push reality of her choice to live a separated life from you and sharing a home where she could experience all the shared times. Holidays are not shared between couples who are D. You want her to see how the future will be without you being there with her.
So, make plans for the kids to celebrate holidays apart from their mom. It may have to be on a different calandar date, but you still have the celebration. Does that make sense?
When you do see her or speak with her, you continue to be polite and even "warmly" if possible, but you do not allow her to take advantage. You are friendly, but not friends. This gap needs to happen in order for her to see the reality of what she has done. She thought you would continue to be her buddy while she pursued a different life. I don't think she ever thought you would cut her out of your life. And, that is exactly what she needs to think. "F doesn't want to be with me". "What have I done?".
Of course her emotions will run every which way before she starts considering moving back. Long before that happens, she will start taking relationship temperature checks just to assure herself that she still has you in her back pocket, emotionally. But, that is a ways off.
This will not be the easiest thing you've had to do, but I believe you will be a little surprised to discover the strength you will gain from this plan. Keep your eyes on the goal.
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!