"And then it turns out that Huntington's "Orthodox civ", while nominally Christian, is much closer to Islamic and Sinic civilizations than to anything else."
Here I would argue with Huntington. Definitely Orthodox Russia as Orthodox Byzantium created after split of Roman Empire into two, developed as despotic civilizations. Nevertheless, Islam still destroyed Orthodox Byzantium and Orthodox Russia was at war with Islamic Ottoman Empire.
In the end, Christianity "both lungs" (as John Paul II proclaimed), will need to unite for Christian Civilization to survive.
So what? In the "international of despots" there are - bound to be - squabbles and fallings out now and then. When the whole world had nothing but despotisms, great and small, were these despotisms at peace with one another? At peace - no, in kinship - yes. What is claimed is that they have more in common with one another than with anybody outside the circle.