Good questions, mackerella.
About this bit:
Because otherwise we're perilously close to concluding again that all Republicans are selfish, and I don't really want to go down that line of argument again...
I think we just don't take the bait of imagining that all Republicans are like Bannon, or are alt-right.
Rod Rosenstein, for example, is a registered Republican; Jim Comey has been for much of his life, too. Neither appear to share all (any?) of Bannon's values or intent.
And this is generally true. I don't even know how most of my friends vote. We may have similar values, but differ in the best way to put those into action.
I don't doubt that alt-righters like Bannon would love to persuade the moderate middle that anyone who goes for the right-leaning party, the Republicans, is exactly the same as him and he speaks for them and an attack on him is an attack on them... but it ain't true.