Heavy ... finally caught up on your sitch .. I usually am not around much during the wekeend, I might read but seldom post.
So a few things that caught me.
That whole bit about it hurting when she talks to your S, about old things .. dogs and what not. Yeah, my W early on in her crisis did that too, was like she was selling S something she felt he wanted, she would constantly try to buy or talk her way out of the guilt. Take that for what it is, she has some serious guilt she is dealing with .... hence with that remark about you being nicer to her, becoming friends ... its a temp check .. common with MLC ... and yeah .. the more I read your story ... the more MLC parallels I see.
Some things to keep in mind if this is MLC, she will want to cake eat, she expects you to be just where she left you, that whole comment about reconciliation ... yeah they do that. Her checking in constantly ... she is off doing her own thing and the guilt adds up, she wants to believe her family is staying put and not moving on without her, all while she is trying to find happiness wherever it is .. it does not matter at this time how shallow.
So .. the trick for you. Focus on your kids, yourself, GAL and PMA. Set boundaries ... be neighborly and kind but do not allow her to mess with your head. She needs to start feeling that you will be fine and move on regardless of her actions ... be prepared for testing and temp checking along the way. Its a very LONG process.