In "vdankobirdmaskdead.xls" the text refers to "the dead". This is a reference to the victims of the plague right? The reason why I ask is that it is used in singular later ("But the dead is not Simon"), making it possible that it refers to a single person.

"Неси свою стражу" is translated to "Keep guarding". I assume that this is the player asking the NPC to continue to watch over the dead, right?

When it speaks of "spirit", does it mean the soul of a person? I.e. the bachelor cannot bind/connect a soul to a dead body (matter).

Also, how literal do you want the translation to be? For instance, "Здесь нет живых. Это место принадлежит мертвым" is translated to "There are no living here. This place belongs to the dead". While the original translation is understandable (though "beings" should probably be added, such that it says "no living beings here"), a more elegant way of saying it (provided that I understood the intent correctly) would be as follows:
"This place is not for the living, it belongs to the dead."

This file is the dialogues between the player and a Birdmask guarding the door of a dead Adherent. I think it should be redone, as I don't like how dead sounds - maybe "deceased", since the person has died recently... This is the player's answer to the mask. The meaning you've said is right. Yep, soul. Teh words have the same root in Russian, so are often used as synonims. Well, I think that'll do.. The reason for such "missing" words is that Russian is very versatile in omiting stuff without a significant loss of meaning. In most cases it's OK to restore words like that.