What exactly is the "net positive utility"? Where exactly is the zero? For example if we assume that existing is always better than not existing, then all existing universes automatically have net positive utility.

If we assume a Christian model where people will get most of their utility in afterlife, this model would put a limit on Heaven : Hell population ratio. The exact numbers would depend on how many people in Heaven plus how many people in Hell give a total zero utility. For example assuming that positive utility of one person in Heaven is greater in absolute value than negative utility of all people in Hell, this model would say that all worlds where at least one person gets to Heaven will be instantiated. Assuming this, the exceptionality of Jesus in our universe is an evidence for all other people going to Hell.

(Just joking. With proper definitions and priors you can prove anything.)