For the "how we all ended up together" question...
If the idea is that we were all sent on an expedition, then I guess the question is who sent us. We've got a few people who have reason to be around Breland, and not a lot of people with any strong national loyalty, so being sent by the King of Breland as some sort of handpicked team might work. Some sort of collaboration of Dragonmarked houses might also make sense, but we've got a few people who aren't really associated with any house.