The analyses of a text #2

The narrator recalls his adolescence.
His old nurse Pegotty's niece Emily fled away with his best friend Mr. James, leaving her fiance behind.
Mr. James's servant Mr. Littimer told the whole process of it to him and Mr. James's cousin Miss Dartle on the terrace.
The result was, after Mr. James leaving behind Mr. Littimer and Emily at Naples, Emily's mood got worse and worse and ran away from Mr. Littimer.
After Mr. Limittimer leaving, Mr. James' morther Mrs. Steerfoth came to.
Peggotty's elder brother has sought for her niece Emily after her leaving.

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I took the hand she held out with a dignified, unbending air, and it was as calm in mine as if her breast had been at peace. Her pride could still its very pulses, it appeared, and draw the placid veil before her face, through which she sat looking straight before her on the far distance.
As I moved away from them along the terrace, I could not help observing how steadily they both sat gazing on the prospect, and how it thickened and closed around them. Here and there, some early lamps were seen to twinkle in the distant city; and in the eastern quarter of the sky the lurid light still hovered. But, from the greater part of the broad valley interposed, a mist was rising like a sea, which, mingling with the darkness, made it seem as if the gathering waters would encompass them. I have reason to remember this, and think of it with awe; for before I looked upon those two again, a stormy sea had risen to their feet.
Reflecting on what had been thus told me, I felt it right that it should be communicated to Mr. Peggotty. On the following evening I went into London in quest of him. He was always wandering about from place to place, with his one object of recovering his niece before him; but was more in London than elsewhere. Often and often, now, had I seen him in the dead of night passing along the streets, searching, among the few who loitered out of doors at those untimely hours, for what he dreaded to find.
[David Copperfield by Charles Dickens]
1. I'd like to know what "it" refers to.
2. I'd like to know if "them" refers to Mrs. Steerforth and Miss Dartle.
3. And I'd like to know what "for what" means here.
Thank you in advance for your help.