I largely agree with your skepticism. I would go even farther and say that even the 10^80 scenario happens, what we do now can only influence it by random chance, because the uncertainty in the calculations of the consequences of our actions in the near term on the far future overwhelms the calculations themselves. That said, we should still do what we think is best in the near term (defined by our estimates of the uncertainty being reasonably small), just not invoke the 10^80 leverage argument. This can probably be formalized, by assuming that the prediction error grows exponentially with some relevant parameter, like time or the number of choices investigated, and calculating the exponent from historical data.
I largely agree with your skepticism. I would go even farther and say that even the 10^80 scenario happens, what we do now can only influence it by random chance, because the uncertainty in the calculations of the consequences of our actions in the near term on the far future overwhelms the calculations themselves. That said, we should still do what we think is best in the near term (defined by our estimates of the uncertainty being reasonably small), just not invoke the 10^80 leverage argument. This can probably be formalized, by assuming that the prediction error grows exponentially with some relevant parameter, like time or the number of choices investigated, and calculating the exponent from historical data.