How we cite our quotes: (Act.Scene.Line)
Quote #4
What rests, but I reveal
All to my lord? Oh, this base quality
Of intelligencer! (3.2.321-23)
The Duchess has just let slip to Bosola that Antonio's her husband. He knows he's gotta go tell Ferdinand, but he doesn't do so right away, waiting for a moment and wondering what's holding him back. Bosola's just discovered that the Duchess has married (and thereby "rewarded") Antonio for no other reason than that Antonio's a good, worthy man, and thereby realizing the dynamic that Bosola himself both most derides and fantasizes about: the dream of reward for virtue and service. He doesn't want to bring down the Duchess, but his compulsion to fulfill his duty to Ferdinand overwhelms his moral qualms.
Quote #5
Where I am a man
I'd beat that counterfeit face into thy other. (3.5.119)
The Duchess realizes that she's been betrayed by Bosola, who's about to take her to Ferdinand. Bosola frequently draws a distinction between his real self and his intelligencer self, and the here Duchess wants to smash the two together. This two-facedness—between the real and the "counterfeit" selves—is part of the "base quality of the intelligencer" mentioned in Quote #3.
Quote #6
Bosola: Must I see her again?
Ferdinand: Yes.
Bosola: Never.
Ferdinand: You must.
Bosola: Never in mine own shape,
That's forfeited by my intelligence
And this last cruel lie. When you send me next
The business shall be comfort. (4.1.128-33)
Bosola's reached the end of his (considerable) tolerance for evil-doing. He's gotten to the point where he realizes he can't neatly separate his work for Ferdinand from his own set of values and understanding of right and wrong. He can say that he's just doing his job, just taking orders but he knows that his "own shape" really has been corrupted by his work as an intelligencer.