Quote 4
[…] he seemed to stand surrounded by a firmament all bright with beaming eyes. (52.1)
Fagin is at the center of the gaze of the huge mass of people at the trial, and their piercing gaze seems to empty him of any sense of self. The crowd overwhelms him with their "eyes" (with a possible pun on "eye/I" – there are too many "I’s," or too many unique individuals, all focusing on Fagin, so that his own sense of self, or his own "I" is obliterated, and he becomes completely passive).
Quote 5
Not that all this time his mind was for an instant free from one oppressive, overwhelming sense of the grave that opened at his feet; it was ever present to him. (52.9)
Fagin isn’t mentioned by name a single time during the trial scene – he’s always referred to as "he" or "him," so the reader has to infer what character it is (not hard to do). But the effect of that is further to alienate Fagin from the crowd (and the reader), and to make him seem less like an individual with a unique identity (and name), and more like a distant object of interest.