The OBO rule and Early Surender.
If the game you are playing has OBO, with Early Surrender, you make your surrender decision FIRST according to basic strategy or indice number wheather the dealer checks for BJ or not. That is the big advantage of E.S.
If your decision is to surrender, then your hand is completed. If playing by indice numbers and the number calls for a split,only then does the OBO rule come into effect, AFTER you make your Early Surrender decision.
It sounds like you are into the math of the game, so by all means listen to the poster who responded to you ( Don Schlesinger ) and buy his books ( Blackjack Attack #1-2-3 ). I would start with #1 and go from there.
I dont think so, but hopefully you are not confusing Early Surrender with Late Surrender. The strategy plays for L.S. are quite different.