Would the brother-in-law moving to PV be a a good thing? 

No. In all honesty this is probably the start of his next manic episode. He will eventually kill himself if moves to PV. 

What are my obligations through this? 

None. I am very certain that that things will get worse if I (or the husband) try to intervene. The brother-in-law is proud of his independence. It will blow up if we gently move to keep him safe. He will push harder to show us how well he can do on his own.

The husband and I flew down to Santa Barbara for the weekend. It was a work-award trip for the husband. Last year his team was a top seller. So I met and hung out with his coworkers. They are a good group of people. I'm sure everyone was on their best behavior. None the less, I enjoyed myself.