I don't see anything that made you keeper of their mental welfare in your title so leave it alone.
Take a vacation. Bora Bora is nice. They need to work it out.
You need to decide how to handle the its him or me and if it is him
You need to decide if you can be her primary and lose some of the others in your life.
The cats not going back in the bag. Prepare for both so your not hurt.
The whole group needs to stop fucking and work on their relationships more.
But i'm a n00b what do i know?