What does 'had been long settled' mean?
The family of Dashwood had been long settled in Sussex.
(My question) What does 'had been long settled' mean?
Here my ideas.
Solution 1:
I am not sure I follow your diagrams, but to be 'settled' is a way of saying you live somewhere, but with more permanence than the word 'live' might ordinarily imply.
My family and I live in Berkshire. We have been in the same house for 28 years. We know the neighbours well and have friends in the village. We belong to organisations in the local town. Thus we can be said to be SETTLED in Berkshire.
However, as I write, we are living temporarily in Manchester. We have a short-term lease of six months on a small house. We LIVE in Manchester but we are not SETTLED in Manchester. If we uprooted everything from Berkshire and moved lock, stock and barrel to the Manchester area, we would become SETTLED in Manchester.
Jane Austen meant that the family of Dashwood had been long-settled in Sussex. Their living and belonging there had been over a long period.
Solution 2:
It means they had lived there for a long time.