Since I spent my creativity on the last batch of RR questions (the Plague, etc.), all I really feel like answering is Question 4.

4. What do you think happens to those who die in the Dead Marshes?  Are they perhaps trapped there to become some of the “spirits” haunting that place along with the earlier victims (whatever the nature of the apparitions at the Marshes is)?

I think the apparitions in the Marshes aren't "real," as in real trapped feär, but instead illusions (so to speak) made by the sorcery that we know Sauron is very good at. Sauron would have to be far more powerful than I credit him to be if he could hold the "obdurate" feär of the Children of Ilúvatar against their will (and why would any of them, from either the Last Alliance or the Wainriders, want to stick around in the Dead Marshes?). I personally think the spectral things in the Marshes are there to scare off anyone crazy enough to approach Mordor *cough Frodo cough* Anyway, Sauron had no way of keeping the spirits of Men from leaving this world; no Ainu could. They could only remain by divine intervention or if bound by a powerful oath santioned by the Valar, as in the case of the Dead (but this still required divine intervention of a sort).

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“But so bright was Rothinzil that even at morning Men could see it glimmering in the West, and in the cloudless night it shone alone, for no other star could stand beside it. And setting their course towards it the Edain came at last over leagues of sea and saw afar the land that was prepared for them, Andor, the Land of Gift, shimmering in a golden haze.”

—Akallabêth

Nature's first green is gold,
Her hardest hue to hold.
Her early leaf's a flower;
But only so an hour.
Then leaf subsides to leaf.
So Eden sank to grief,
So dawn goes down to day.
Nothing gold can stay.

—Robert Lee Frost