Quote 4
"He wanted you to be the small, quiet girl from Abnegation," Four says softly. "He hurt you because your strength made him feel weak. No other reason." (22.29)
You've just read Four's character analysis of Al: he only wanted to be friends as long as he could be the big protector. Do you think that's a fair analysis of Al? And does that mean that Al's friendship was never really real?
Quote 5
"Because you're from Abnegation," he says, "and it's when you're acting selflessly that you are at your bravest." (24.76)
Oh Four, you're so wise. Here's one of his impassioned arguments about how the virtues of the five factions can work together (to form Voltron). So Tris is braver—and more powerful—when she's being selfless. And her selflessness seems to come from her family. In that sense, her power lies not in her faction identity, but in her personal relationships. And family is something that crosses faction boundaries.
Quote 6
"Taunting you? You mean when I threw the knives? I wasn't taunting you," he snaps. "I was reminding you that if you failed, someone else would have to take your place."
I cup the back of my neck with my hand and think back to the knife incident. Every time he spoke, it was to remind me that if I gave up, Al would have to take my place in front of the target. (24.73-4)
The downside to being in Tris's head (and knowing all of her terrible, terrible secrets) is that we don't know any other people's secrets—unless something happens that gives them a chance to tell Tris. But Four wasn't keeping a secret from Tris when he tried to help her; it's just they saw this from different points of view, so they didn't share the same information.