Avram:
Regarding Yom Kippur, a person has every right to believe that in reality R’ Yehoshua was right and Rabban Gamliel was wrong and in fact you can’t fully believe that Rabban Gamliel was right, because it’s very likely that he was wrong. However the halachic principles tell us that we have to observe Yom Kippur AS IF Rabban Gamliel was right. But it doesn’t tell us anything about the underlying reality.
“but why is it not pashut if it has been settled by the Jewish people at large?”
Because we have no way of knowing if the Jewish people settled it correctly.
“This is consistent with our belief that Hashem guides and protects our people, and brings us close to Him”
1) So why didn’t he protect those who disagreed with the Rambam?
2) If we will be excused then there is nothing to be protected from so G-d does not have to intervene.
“Since this status is in our hands, I don’t think your step 8 works.”
I was principally talking about his actual status, not his societal status. But even regarding his societal status, if I am correct then if someone legitimately can’t completely believe something then perhaps he shouldn’t get the societal status either.