Somewhat OT: the last part seems wrong at first glace. I hope that feeling only reflects my biases, because the argument could explain why an entity capable of affecting distant Everett branches -- say, in order to prevent the torture of sufficiently similar entities -- would have left no visible trace on our own timeline so far.
(In the cheerful interpretation, which assumes something like Mangled-Worlds, said entity has enough fine control to not only change branches that would otherwise lead to no entity-level intelligence, but also to undetectably backup memories from every branch that would discard unique memories.)
It seems on second look as if the argument might work -- at least if the entity doesn't refuse to update on the existence of someone who can form a belief based on the evidence, but only ignores some other facts about that entity. Then the answer it arrives at seems to have a clearer meaning.
I'm not sure what you mean by most of this. What is the "last part" and why does it seem wrong? Why do you hope that the idea presented in this story is correct? There seem to be too many factors to determine whether it would be better than some unknown alternative. What does this have to do with many worlds/mangled worlds? The story would still work in a classical universe.
Suppose we could look into the future of our Everett branch and pick out those sub-branches in which humanity and/or human/moral values have survived past the Singularity in some form. What would we see if we then went backwards in time and look at how that happened? Here's an attempt to answer that question, or in other words to enumerate the not completely disastrous Singularity scenarios that seem to have non-negligible probability. Note that the question I'm asking here is distinct from "In what direction should we try to nudge the future?" (which I think logically ought to come second).
Sorry if this is too cryptic or compressed. I'm writing this mostly for my own future reference, but perhaps it could be expanded more if there is interest. And of course I'd welcome any scenarios that may be missing from this list.