Why shouldn't we be grateful to the totality of our ancestors for getting us this far? Who is to say that we could change even a butterfly wing's flutter of the distant past and still have everything turn out as now?

b)I am specifically claiming that while "nothing means anything" is the--lie that tells the truth--summation of nihilism it, by it's very nature, doesn't imply a course of action. So it doesn't matter how metaphysical of a claim it is.

You know nothing, Jon Snow!

b) If I understand you correctly, I think you're sneaking the assumption of nihilism back into your argument. The "lie that tells the truth" could also very well describe "everything means something," since I undeniably experience meaningfulness as something and not as nothing, despite all scientific facts. Just as I experience you as another soul though I know you are "just" matter. And this undeniable experience of meaning would undeniably imply a course of action. Non-harm (not treating a soul like an object) most immediately coming to mind.