I always thought it was a gradual and incremental process beginning (unofficially) before 1054. Then when? That is what I can't seem to tack down. Where do our traditions finally, and authoritatively end?
I haven't read the whole thread, but what I gather from my reading and personal study there really is no hard line date. I've always read and been told that the 1054AD date is a way to tidy up Church history just so there is SOME sort of official moment in time we can point to. But From what I gather, most historians have said or written that both East and West, on the parish level were still "in communion" well after that date, despite the mutual excommunications, especially in the middle east. I'm not a professional historian or anything, but that's what I've read and how I understand this issue. IMO 1204AD is probably a better date for our split on a practical
real world level. I think once those events transpired, the East looked West and said, "woah, who are these people, they're not with us because they just sacked the city"! (not saying the East was right or wrong, or the West was right or wrong, only that that was probably how most in the East felt at that moment) So in reality I think that is probably the real moment of the split, the 1054AD is "official" but I doubt it affected very many Christians or churches...it was more of a heirachical event at that point I think. 1204AD brought it down to our level (by that I mean us on the parish level). Again, this is what I've read and have been told and I can't really point to any one source, but it makes sense to me. More sense than the idea one morning we're united and the next we're not. it might work like that NOW with modern inventions like telephones, and internet, but I find that hard to believe it happened that way 1000 years ago.
However personally, I still suspect even after 1204, there may have been some sort of union in some locals, I'm not sure there was a complete and truly finalized break between East and West until the time of St. Mark of Ephesus and those events. At least up until then, I think there was "hope" one side or the other would "come home" as it were.....but I I think after florence, both East and West looked at each other and didn't really recognize their tradition in the other side anymore. So by then i think the rift was complete. But that is my pure speculation and my own PERSONAL opinion on the matter.
I've also read the rift happened way before 1054, but again I think that puts too tidy of a date on things....the split was gradual and took centuries, and I don't think there truly is any single date or event we can point to and say "it was 100% complete" at that point. Again, just my opinion. Maybe the historians can give you more help.