The names of the righteous are recorded in books.
Isaiah's wife (who was also a mother) must have had some great spiritual strength, to be called a prophetess (Alma 32:23). Or the designation could simply mean "wife of a prophet".
The spoils of Samaria are the conquered people and wins from the campaign against Israel. 2 Kings 15:29, "carried them captive to Assyria".
In the New Testament, the Lord sent a blind man to wash in the pool of Siloam, and he was healed. The wathers of Shiloah must have been a commonly known geographic location, for it is referenced a few times (John 9:7,11). I imagine it was a peaceful place.
Isaiah is using an analogy of bodies of water. Because Judah has rejected Jehovah ("the waters .. that go softly"), they will be flooded with a river (Assyria) that will overflow its own boundaries and cover the lands.
I like the way he describes it:
It is interesting to note the differences in punctuation in 2 Nephi 18.
I wonder why he says "even the king of Assyria and all his glory." Why does he mention the king, and not just the nation? Was he a notorious leader?
The Assyrians will come upon Israel first and then Judah.
I can see where the Jews would adopt the attitude over the years that Jerusalem could not be destroyed, since here is a prophesy that clearly states that it shall be saved.
The Lord is telling Judah not to associate with other nations, or form alliances. He will protect them by His own power.
Do not trust in the arm of flesh – your mighty counsel and earthly wisdom will not stand against the power of the Lord (D&C 3:6-8).
The Lord is telling them, again, not to make any political alliances, or to depend upon the methods of other nations, but to wait upon the Lord. In that context, that commandment could be too much for the people to believe in, and be a real stumbling block of their own day.
The Lord's kingdom is not a political one, and he does not need political allies to help him win the battles.