Hey M. It sounds directionally correct for you to "up the ante" towards D as boundaries are broken. Be unyielding on that path because you deserve better. As someone said in relation to my situation, people can and do reconcile later if/when the alien releases our partners. I told my D13 that it "ain't over until a judge bangs down a gavel" and that, if W reconsiders and honors my boundaries, I'm open to resuming work on the marriage. I'm also fine moving on because I'm conident I'm doing lots of things right for myself and D13 at this stage.
It is too bad about your BILs. They are her family and often that bond trumps all others, though I have close friends who are closer to me than my step-brothers and half sister. Still, it was a betrayal of you and your trust. Ideally, they'd focus on what's best for your kids or, at worst, they'd remain neutral (don't encourage or discourage the situation).
I'm glad your expanding your social circle. One thing I'm wondering, especially given your comment about breaking down at one point, is how comfortable are you with being alone. Self-soothing is an important skill so that we don't lean too much on others for comfort. It is also a great skill to teach our kids. I hope you're investing some time to work on being comfortable on your own too.
