It's been a year, but I finally wrote up my critique of "longtermism" (of the Bostrom / Toby Ord variety) in some detail. I explain why this ideology could be extremely dangerous -- a claim that, it seems, some others in the community have picked up on recently (which is very encouraging). The book is on Medium here and PDF/EPUB versions can be downloaded here.
Agreed.
Yeah this seems right, maybe with the caveat that Will has (as far as I know) mostly expressed skepticism about this being the most influential century, and I'd guess he does think this century is unusually influential, or at least unusually likely to be unusually influential.
And yes, I also agree that the quoted views are very extreme, and that longtermists at most hold weaker versions of them.