The Orthodox position is that Rome split from us, not the reverse, so I can't directly answer your first question. The issues that lead to the split were, in the main, Papal claims to supremacy over the Church (which none of the Eastern Patriarchates would accept) and the unilateral addition of the filioque into the Creed. The direct cause of the Schism, initially, was the excommunication of the Patriarch of Constantinople by Rome, which is why it is conventionally dated to 1054, but this is merely convention. There had been tensions earlier and a schism which was later healed (what you call the 'Photian Schism', though we would not agree that St. Photios caused it) so it's plain that the estrangement began in the first millennium. I'd also suggest that it wasn't really cemented until much later with such events as the 4th Crusade and the Palamite Councils playing their part. I guess I'd view it more as a long process than as a single event.
James