I respectfully disagree. Introducing the Balrog in RoP too early has presented more opportunity to go off canon and thus present further complications that the "show runners" now have to address.

Knowing that there is a Balrog lurking is not something easily forgotten by dwarves (who documented quite a lot) and so there wouldn't be incentive to mine greedily or too deep. When one break to the well-established canon occurs, suddenly many problems arise and thus more breaks to the canon occur to rectify it. The introduction of the Balrog was simply a 'memberberry. At least they visually did the Balrog justice (by imitating the movie's perfect design).

Woody.

Rhûn is in the East, it is not in Mordor, it is it's own location.

Your quote does not mention Lothlorien at all, it refers to Greenwood (later known as Mirkwood).