OMG Muddle, are you a puppet-master to this woman. Does she experience ANYTHING in her life that is not directly caused by you? Seriously, reading your posts, this woman is more into you than most of our wives ever were or ever will be. She seems totally dependent on you for everything, including her feelings.
Geezus. Muddle, I think for her sake but mostly for YOUR sake, you need to step back from this process and REALLY look at how you interact with her. You need to give her a chance to see how she actually lives without the emotional umbilical cord you provide all her feelings and emotional well/mal-being through.
I think you do this by refusing to get into conversations that involve how she feels because of you, or how she feels because of what you did, say, or plan to do. If she says you're being selfish again, agree with her and then walk away. If she screams at you, let her. She's obviously going to blame you for everything no matter what anyway so why not just stop trying to explain yourself. Stop validating her. Stop INVALIDATING her. Stop participating in the situation where you do either.
You asked how she will change from being this way. Well, I can't answer that, but I can say that what you've been doing hasn't worked so maybe it's time to change something in you instead of trying to change something in her.
Stop trying to understand her, even if it's for the purpose of validating her. Stop falling into her emotional traps. Stand strong and realize that your son may go through some stuff but YOU can help make that better by being stable and "even" when it's obvious that your W is not going to be for awhile.
Then, maybe after some time has past and she can look back at you without the sh!t colored glasses, i.e. she learns that life is crap without you as much as with you , then maybe there will be room and impetus for change. Until then, I think she will likely just keep leaning on you literally until the day you walk away...because I doubt she ever will.
Muddle, you know I don't say these things lightly. I am ALWAYS the last one to say walk away, and I am not really saying that to you, but on some level, I think you have to in order to truly give her the room she needs to change...or not.
, then maybe there will be room and impetus for change. Until then, I think she will likely just keep leaning on you literally until the day you walk away...because I doubt she ever will. 
