sorry to hear about your sitch. i noticed something though in reading your post. first, she says you have to file, which means she can't bring herself to do it for whatever reason. then in the texts about meeting to discuss the d, she says something to the effect of we shouldn't carry this on any more then we should, should we. she questions her own statement at the end of it.
both of these things show me that she hasn't made a decision. she might be with the om, but if she wanted to fully commit to him then she would file. she hasn't let go of you yet.
i guess this puts you in the drivers seat, you can keep db'ing or file. i don't agree with the controling the d by filing first. you will have a chance to respond and bring your case and refute what w is claiming or asking for. but you will need cash to do that with counsel. i would start a rainy day fund now, and if it happens your prepared.
my advice is keep doing what your doing, let her have her space, and just be you and enjoy the parts of life that you able to for now.