So I wanted to ask a halakhic question. Is the Rabbi considered a heretic?

Ask first whether the Rabbi even gives any importance to classifying someone as a heretic..

Considered by whom? Ask whoever it is whose opinion interests you.

Granted, he asked you because your opinion interests him.

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In Sanhedrin, chapter Helek, it is claimed that you have no share in the World to Come.
Do you think that is the case?
By the way, similarly, you also said that you are not sure of the existence of the World to Come.
How does that fit with the Mishnah + the Talmud?
And likewise regarding all the other similar topics where you said that they are based on prophecies and therefore you cannot trust them.

I debated whether to delete this, but because of my sensitivity to censorship I’ll give you another chance to phrase your questions properly.

The Talmud and the Mishnah mention the World to Come and resurrection of the dead many times, and there they are pretty important. If these are concepts about which nothing can be known, then can one also not rely on the Mishnah and the Talmud on these matters? If so, the whole reliability of these sources is undermined.

I do not deal with the reliability of the Talmud, because that is not important.
It is an authoritative source in matters of Jewish law.

And where does the authority come from that distinguishes between Jewish law and aggadic literature?

I did not understand the question. Are you asking where I get the authority to distinguish? I have no authority whatsoever, and I never asked you to obey me.
My position is that the authority of the Talmud is in the halakhic realm and not in other realms, and if you want you can accept that, and if not, then not.
I say this for many reasons: 1. Because that is the only thing for which we accepted it. 2. Because it is impossible to define formal authority in other areas. 3. Because in other areas they have no better understanding than I do, so there is no substantive authority. 4. Because in other areas the statement itself is not clear (it is not clear what this or that aggadah means).

1. No one ever said that the purpose of the Talmud is only Jewish law, and the presence of aggadic material there is sufficient proof that it is not.
2. The aggadic material does not need authority to convey some message to us. One could similarly say that whatever is found in the Torah and is not commandments has no authority or purpose, but stories appear there too, and their presence in the Torah indicates that they have a purpose.
3. If I’m not mistaken, both in Jewish law and in aggadah the Sages simply bring information they have, analyze it, and draw conclusions from it; in both cases the level of understanding is fairly similar.
4. There are interpretations, as perhaps in any area of Torah that is not fully understood.

All right, I wrote briefly what I had to say, and these questions are not relevant. You can read more at length in the second book of the trilogy.
I’ll address your questions briefly and conclude:
1. I explained that it is impossible to establish authority over aggadic literature. Its presence there says nothing.
2. Aggadic passages may try to convey a message (though usually they will not succeed). The question is whether the message is clear and whether it is binding.
3. That is simply not true. In aggadic literature there is no information and no analysis. It is a collection of stories with one message or another.
4. Aggadah is not an interpretation of anything. It is the product of whoever wrote or said it.