I have to say that Dorico's Flows, Layouts and Players will (in the future) be very powerful and make this kind of thing very straightforward.
However, for the time being, Finale still has much to commend it. For complex works, I usually create a "PARTS" file, which is duplicated from the finished full score (using ScoreMerger to join separate documents if necessary).
That way, I don't have to worry about the score being messed up by alterations to the parts. I can also have a running head that includes the part name, whereas "Score" in the full score is a bit odd.
This may seem like a duplication of labour, but actually, it gets the best of Linked Parts and separate docs.
Also, titles of movements need to be either Expressions or Measure-assigned Text, because they will appear on different pages in different parts.
Not sure about your unlinking problems: might need to see a document.