Your choices remain irrelivent. Say your CoC never did the main quest, thus never stopping Dagon, thus ensuring the destruction of Mundus. Well, that never happened. That 'Potential', for lack of a better word, never coalessed into reality. Your Dragonborn never fighting Alduin is irrelivent, because it serves as an unreality in the Elder Scrolls Universe. The Nerevarine faced Dagoth Ur. The CoC found Martin and together they defeated Dagon. The Dragonborn WILL face Alduin whether you like it or not. There isn't any choice in the matter, even if your gameplay gives the illusion.
Likewise, a hero doesn't get to decide if the Blackwood Company is destroyed. It happens, whether you (the player) like it or not. Heroes are tools of change, but they are not free agents within the universe, only within the limited game-play representation of it.
"All sources indicate that you will fail. It is a certainty. However, I also predict that this will not stop you from trying." Dyus knows that the Champion will try, but that the logical conclusion is for the Champion to fail. That has nothing to do with madness vs order.
Also, why was the same forethought and prediction power that was able to predict the outcome of a Dragon Break not able to predict something as mundane as making a staff?.
Now, Logic IS order. Madness, by it very definition, defies logic. The Priests predictions are based entirely on logical conclusions, and thus cannot take into account the inherent instability of Madness. By this time, the CoC has already become Sheogorath, and Sheogorath has become the CoC, rendering all the predictive powers of the Priest of Order irrelivent. Again, it is the total inability to predict the outcome of madness which allowed for your success, not some inherent lack of destiny on the part of the Hero. To word that differently, the CoC's capability in recreating the staff was a logical impossibility. But the CoC was not a being of logic, at this point, rendering any attmpts to reason through to predict an outcome totally moot. Without the abilty to reach logical conclusions (because the situation and the individual involved were illogical) the Priest of Order may as well have said you were going to make jelly toast, it would have made as much sense.
And Dragonbreaks are actually very predictable cause-effect events which can be predicted by those who have sufficient knowelge. The Dunmer predicted the Alessian Dragonbreak, the Khajit predicted the Dragonbreak when the Numidium was first activated by Tiber Septim. If you understand magic and the forces of creation, predicting Dragonbreaks is easy. Of course, few mortals understand such to a sufficient degree, so it seems spontaneous and erratic to the teeming masses.
Finally, again, the CoC is no longer around. When you Mantle something, you don't stick around as whatever you became, it replaces you utterly.