In "Six Months Earlier" Nathan was prepared to go after Linderman before the accident

I maintain that that was more about establishing his own autonomy than out of any sense of civic duty. It is an arguable point, I'll admit.

Nathan also cares deeply about his family

Oh, he certainly does. I just think he cares about them in the sense of "valuable property", and is often frustrated at his lack of control over them. Again, reasonable people could interpret his actions differently, but that's how I see it.