Since you still don't know if this is what you want DO NOT move in with him and his girlfriend. What would you do if you decide you want to be monogamous, he doesn't, and you two break up?
I'd stick with your plan of moving to the city for work but keeping your own place until you know what you want.
Woodsmith: My husband
Merry: Tig's wife/slave
NT: Merry's boyfriend/owner
Elle: NT and Merry girlfriend
Umbra: Elle's Dom
Pet: Umbra's slave/wife, Elle girlfriend
Domo: Pet's submissive