Reward and punishment, Gan Eden and Gehenna, also aren’t written in the Torah, and not even in the prophets, at least not explicitly. What is the Rabbi’s position on that? And if that too is unclear, then what exactly is the point of serving God if I’m working for nothing, when there is no redemption or reward and punishment..

The same thing.
First, I didn’t say there isn’t. I said I don’t know. Second, we don’t serve for the sake of reward. See Maimonides, beginning of chapter 10 of the Laws of Repentance:
Law 1
A person should not say: I will fulfill the commandments of the Torah and engage in its wisdom in order to receive all the blessings written in it, or in order to merit the life of the World to Come; and I will separate myself from the transgressions against which the Torah warned us in order to be saved from the curses written in the Torah, or in order not to be cut off from the life of the World to Come. It is not proper to serve God in this way, for one who serves in this way serves out of fear, and this is not the level of the prophets nor the level of the sages. And God is served in this way only by the ignorant, women, and children, who are trained to serve out of fear until their knowledge increases and they serve out of love.
Law 2
One who serves out of love engages in Torah and commandments and walks in the paths of wisdom not because of anything in the world, and not out of fear of evil, and not in order to inherit the good, but does the truth because it is true, and in the end the good comes because of it…

I know there is an ideal of reaching service out of love, but it’s supposed to be based on the idea of reward and punishment. Otherwise I don’t see any real reason to serve… or more than that, why love God? In the end it has to start from some kind of recompense, otherwise there’s no reason for me to change my way of life because of gratitude for the fact that He created me..

I explained this at length in my trilogy. The obligation to do what is right does not depend on recompense. Just as the obligation to be moral does not depend on my receiving some reward for it. Do I refrain from murder or theft because I’ll gain something from it? Is there no expectation of a secular person not to steal and not to murder, even without the sanctions imposed by law?
Truth is the best reason, and it needs no further justification. Observing the commandments makes the world better (in some spiritual sense), and that is the reason to do it. Besides, it gives our lives meaning and a system of principles for analyzing life and the world (I won’t elaborate here).
If someone finds it difficult to keep the commandments without recompense, then the stories about reward and punishment were meant for him (assuming these really are unfounded stories). That is a question for a psychologist, not a rabbi. It does not lie on the plane of values but on the psychological plane.

To tell the truth, I’ve never understood the mindset of a person who upholds moral values that limit his freedom and desires when they add nothing for him. The reason I care about values is because it’s good for me, or because of religious commitment, or because I was educated not to steal, and if I steal I’ll feel very bad with myself, so the pleasure from stealing is no longer worthwhile for me; and maybe also because I won’t steal so that others won’t steal from me—in other words, it pays for me to believe in a value for the sake of a social convention that benefits me. True, it seems to me that this is only the reason for values. Today I keep values because I feel bad violating them. I love meat, but I feel so disgusted when I think about the suffering the cow went through before it reached my plate that it already doesn’t taste good to me, and personally I don’t eat it. But I don’t see that as making me more truly moral, in the real sense of things; and I even recommend that others not watch things about the suffering animals go through, so they can keep enjoying it. That also seems to me to be the rational way to look at values, and therefore I was surprised by what the Rabbi wrote in favor of veganism… isn’t that so?
P.S. Does the trilogy include the notebooks on faith / belief that the Rabbi has on the site, or is there no connection?

If so, then that is our point of disagreement. In my opinion, not all actions are self-interested (several columns were written here about that, and the talkbacks discussed it too).
A revised version of the notebooks makes up the first book of the trilogy.

If the Rabbi could send clear links, because I didn’t find anything comprehensive on the matter… In any case, I’m also not claiming that everything is interests, only that a person is born with natural / acquired feelings toward immoral things. Every normal person has a bad feeling and a kind of inner disgust toward murder, and therefore he will refrain. But in serving God that seems irrelevant to me..

See column 120 (and a bit of 122) and onward.

Those feelings, if they are the motive for action, are exactly like an interest. You do it for the benefit (a good inner feeling). In last night’s Zoom lesson I briefly addressed this distinction.