`We need a state religion that is compatible with elite fertility, or else whites will disappear and the remnants will be wiggers.
Orthodoxy has the great advantage of being a coalition of national faiths.`
Orthodox fertility rates are below Catholics, Protestants, and those that identify as having "no religion", even excluding population growth among non-Orthodox in the third world. They are the least likely group to have more than two children: https://www.demogr.mpg.de/papers/working/wp-2006-013.pdf
Boosting the White population seems like a horrible reason to join the Orthodox church (or any church, for that matter) -- if fertility is a primary factor, it would actually do more harm than good. Jim's take is typical of many on the right who care very little about theology but just want an organization that overlaps with political beliefs. "Red pill" first, theology second.