[The Squatter of Amon Rûdh]

and that the Shire basically means "the Neighborhood". (Makes sense if you think about it, but I never had.)

To an Englishman it means more than a neighbourhood. Quite a few of our counties' names end in "shire", and Tolkien has thrown elements of various counties, both North and South into the hobbits' country. Yorkshire, for example, was divided into Ridings, an old Scandinavian division into thirds, in JRRT's day (recent governments have divided the county up, like the philistines they are, to create more seats in parliament); Berkshire, where I reside, contains towns called Newbury and Bucklebury, which might sound a bit familiar and there's a place in Hampshire called Micheldever. It's almost as though JRRT was trying to gather together all of his favourite country towns and put them beyond the reach of railways, housing estates and tarmac.

So, what makes the difference between being heroically or foolishly "fey"? Does it lie in the personality structure of the one affected? In the situation?

It's a matter of how appropriate the mood is to the situation and what action it leads you to take. If the situation is hopeless and the mood causes a great act of self-sacrifice that saves everybody else then it's heroic. If it causes an unnecessary and futile sacrifice then it's criminally stupid. Then there are shades of grey in between.

"Doom". You get such a sense of inexorable fatality with this word when reading LotR that you don't get from, say, hearing C3PO say "we're doomed" every five minutes.

That's because not one of Tolkien's characters is a neurotic android who camps it up constantly.