Answer

B., hello.
It is hard to understand what you are writing. In the future, try to phrase things more clearly. I will answer based on what I understood from your words.
We are accustomed to the idea that the Sages have authority. We do not depart from the Talmud in the realm of Jewish law. One must discuss (investigate) the reason for this. One can see this as essential authority (they know everything and do not make mistakes) or formal authority (we accepted their authority upon ourselves). I tend toward the second possibility (and so too in Kesef Mishneh, chapter 2 of the Laws of Rebels). The Sages were human beings like you and me; they could make mistakes, and one can see in the Talmud that they indeed made use of that ability more than once. To the best of my understanding, this can happen both in Jewish law and in thought and in assessing reality, like with any person.
But a halakhic ruling in the Talmud is binding because that is the law. Exactly as the laws of the Knesset are binding—not because they are always correct, but because that is the law. We accepted upon ourselves the authority of the members of Knesset.
Now we must discuss the factual determinations of the Sages. Suppose they determined that the earth is shaped like a box (such that passing by its two sides is twilight in the evening and dawn in the morning). Someone who thinks they are always correct (they have divine inspiration, etc.) will presumably think this about factual determinations as well. But I do not belong to that camp, and therefore in principle they may have been mistaken. So what follows? My relation to their factual determinations is different from my relation to their halakhic rulings. The reason is that there is no formal authority—as opposed to essential authority—regarding determinations of fact. The problem is logical: authority in the realm of facts is an internal contradiction. After all, once I have concluded that the earth is round, one cannot require me to think that it is square because the Sages have formal authority and determined this. I might perhaps say the words “the earth is square” with my mouth, but in my heart I do not believe it unless they persuade me. Formal authority operates with respect to action and does not require persuasion. But regarding facts, without persuasion formal authority has no meaning. One can require me not to sort on the Sabbath or to cross the street only at a green light, even though I think there is no prohibition in this. But one cannot require me to think X when I actually think that X is not true (that is, when I think “not X”). That is simply a logically contradictory demand.
My claim is that the world of thought consists not of norms but of facts. Intellectual principles such as divine providence, the existence of a World to Come, and the like belong to the realm of facts (either there is providence or there is not; either there is a World to Come or there is not). Therefore here too, as with the shape of the earth, there is no place for formal authority. If I were convinced that the Sages had information that I do not have—that is, that they have essential authority—I would accept their words. But that would only be because I had become convinced that this is the truth. As long as that has not happened, formal authority is not defined with respect to facts.

Now to your questions. Since the statements of the Sages about the World to Come and other metaphysical claims seem speculative to me, and I have not been convinced that they have a clear source (a tradition from Sinai), I have no position regarding them. I do not know whether there is a World to Come or not. The fact that the Sages think so does not change my view, because there is no formal authority regarding facts, and I have not been convinced that they possess essential authority (that is, knowledge).

As for the survival of the soul, that דווקא seems plausible to me. As a dualist who believes in the existence of a soul or spirit, it seems plausible to me that this remains after the body dies. Where it goes at that stage, I do not know. But here too this is only my own reasoning, not because the Sages said so, and I cannot be certain of it.