If I understand the article correctly:
In order to ground my position, I have to understand the other side’s starting point and the depth of its arguments, without bias. Only from there can I understand whether he is in fact “locked in,” and then my claims are actually valid with regard to him as well.
The question is whether this is a practical option for a young and unskilled boy? (Not that it’s trivial for an adult either.)

Only he can determine that. If he feels that he cannot do this right now, he should suspend the decision until the stage when he feels capable of doing it. He doesn’t have to make decisions now. It takes time to think and form positions on issues like these.
I’ll just add that making decisions does not require plunging into the full depth of every option on earth. We don’t have time for that, so it also isn’t required. One has to make preliminary decisions about what can even be considered, and only regarding what remains should one go into a deeper examination.

Since he isn’t present in the discussion, I’ll allow myself to answer in his place: he still isn’t ready for this logical level.
So my question is whether it’s possible to provide him with something as first aid.
For example, he told me that it’s especially hard for him when he gets to theoretical issues that require analysis and precision, and then the nagging question pops up: maybe none of this is true.
I’m of course bringing this only as an example.
If I broaden this into a more general discussion, what can provide an immediate response for a person who knows how to ask the sharp questions, gets to the point where they trouble him, but still doesn’t yet have the tools to answer them?

I don’t know. That’s an educational-psychological question, not a philosophical-logical-Torah question. If it bothers him very much, then in my opinion he should take a timeout, get into the issue, and examine it now. I suggest he read the column I sent you, and then it will be possible to talk with him (you, or if you want, me).
It is indeed said, “As for the one who does not know how to ask—you open for him,” but if someone knows how to ask and does not know how to answer, it seems to me that one should answer him.

First of all, thank you very much for being willing to talk with him! I’ll see where things go with him, and I’ll come back if needed.
As for the matter itself—and this is now regarding myself—I’ve been troubled by this problem for years, and I feel that it actually is a “philosophical-logical-Torah” problem. I’m not familiar with any structured body of proofs for the truth of the Torah’s path, and it also doesn’t seem that the Torah itself is troubled by this issue. “And you shall tell your son” seems to me to somewhat close off the opportunity for self-examination, certainly for the masses. It is also very hard to free oneself from the burden of the axioms that education instills in order to reach a clean and unbiased place that can examine the issue properly.
That is, the Torah does not really place before most people a ready basis for inner examination and choice, but rather plants a person psychologically somewhere deep inside a very, very specific side.
Full disclosure: I already asked the Rabbi a similar question some years ago. I would absolutely accept an answer of “take it from there” 🙂

Obviously, what I wrote—that this is not a logical-philosophical-Torah problem—was in relation to the son’s problem, who knows how to ask questions but not how to look for answers. For someone who does know how to look for answers, this is of course a logical-philosophical-Torah question.
The column I sent you to explains why the claim that others think differently is not an argument. If you simply want to examine your religious outlook, not because others think differently, I can suggest my book The First Existent. It’s hard to carry out such a long and complex move here in a thread.