What do we actually see here? What is the connection between the claim that every true thing is alluded to in the Torah (in Maharal’s homiletic / analytical style), and the claim that everything in the world is in practice alluded to in the Torah? And if people mistakenly think that even ideas that are true in their own eyes come out of the Hebrew Bible through interpretation—not through derashot—that is not our responsibility.
[And by the way, it seems clear that Maharal is referring only to aggadic derashot, which are what he dealt with throughout this entire “Well” (except for the final exposition, “this master has no money, that master has money,” and at the end appears the quotation cited in the question, that all derashot are merely asmakhtot; but it seems obvious to me that Maharal is not saying that the Torah-level law that money effects betrothal, and that the money goes to the father, originates in “the view and intellect of the Sages” even before the derashah. Rather, these remarks of his—that derashot are asmakhtot—apply only to the aggadic derashot in the rest of the “Well”). However, it still requires investigation whether the relation between Maharal’s explanations and the Sages’ intent in these derashot is that of a regular asmakhta, or an asmakhta in the Maharalian sense.]

* true in their own eyes

Let me make a few comments:
0. My remarks too were about aggadic midrashim.

1. What you write reminds me of a story I already told about my friends at Netivot Olam Yeshiva. When they saw that every day at noon I went to the university, they argued to me that everything is found in the Torah. I told them that my answer is twofold: a. If so, then what’s the problem with my going to the university? I am learning Torah there too. Does the place make the difference?! b. Please, be so kind as to meet me at “Oferon ben Tzohar” and find for me in the Torah the solution to Schrödinger’s equation for a rotating potential well, and then I really will be able to stay in yeshiva and not waste my time at the university. Needless to say, I still haven’t received their answer (I have meanwhile found it myself in more conventional ways). Similarly, you are claiming here that only correct things are found in the Torah—but we have no way of knowing what is correct and what is not, and what is found there. That is a claim that cannot be refuted, and in my opinion it says nothing, at least on the practical level.

2. Even according to your approach, what is certainly written here is at least my claim that one learns nothing at all from the Torah; rather, one inserts one’s own ideas into it.

3. Beyond that, one can indeed infer from here that you can insert anything into the Torah. If something seems right to me, then it cannot be absent from the Torah, and I can force it in there by various crooked and bizarre methods. What is that if not the claim that you can put into it anything I think of?! True, the responsibility for the mistake is not ours, and nobody said it was. Still, it is written here that you can derive everything from the Torah.
So from points 2–3 it follows that both of my claims really are written in his words (and of course they are connected): You learn nothing from the Torah. You can derive everything from it.

4. Indeed, in Maharal’s “analytical” style you really can derive anything from anywhere. Even general relativity from Tzafiffo.

[I can’t really argue, because personally I don’t connect to Maharal’s explanations, and from my impression it seems to me that his relation to the words of the Sages is that of a regular asmakhta in the usual sense—that is, there is no real connection at all, as you write here.
By the way, Malbim in his generation was like Maharal in his generation and found other ways to “explain” the derashot, except that Malbim on the Hebrew Bible did the same sort of verse-stuffing even in interpretation itself and not only in derashot; and it is really about him that your broader claim applies, the one dealing with interpretation of the actual biblical passages. It’s just that what still stands before me is that intelligent people, from whom I once heard many things that at the time seemed illuminating to me, though today I do not remember them at all and perhaps they had no real value, greatly praised the above—for example Rabbi Meir Mazuz on Malbim, and Rabbi Nachum Broida on Maharal (many learned from Maharal and created on his basis, and the above-mentioned Rabbi Nachum Broida was also one of them, like his teacher Rabbi M. Shapira).]

A question about asmakhtot. Eruvin 54: Rav Chisda said: Torah is acquired only through mnemonic signs, as it is said, “Put it in their mouths”—do not read “put it” but “make signs for it.” Rav Tahlifa heard this in the West and went and said it before Rabbi Abbahu. He said: You there derive it from there; we derive it from here: “Set up markers for yourself”—make markers for the Torah. [A search for “we derive it from here” turned up six instances in the Talmud that tell of differences between the sages of the Land of Israel and the sages of Babylonia regarding various asmakhtot of this kind.] In Maharal’s way, I suppose they would find in each such asmakhta a different “aspect” of the shared content, and then it is understandable why they make a whole issue out of “we” and “you.” But if these asmakhtot are only memory aids, then why does it matter where you hint to it from? Are these stories just incidental? Or perhaps the point is only to see which asmakhta sounds smoother and sharper, the way people look for the simplest possible practical difference.

Maybe this way and maybe that way. In my opinion, asmakhtot are like derashot nowadays. They are not merely memory devices, as people tend to think (because usually they don’t really help one remember); rather, they are meant to give flavor to the ideas, the way preachers do. So they offer different asmakhtot in order to glorify the Torah and make it pleasing. Not my cup of tea, but quite a few people are moved by such derashot.

Seemingly they do help someone remember, if he is used to biblical verses (which were written and widespread), because then either when he encounters the verse he will remember, or in general, when you connect something to something familiar—even artificially—it helps one remember it itself. I think that is my own sense, though I’m not sure.
For example, I have a few asmakhtot that really stuck with me, and I always remember them when I run into the verse or by means of it, such as “The deceitful man will not roast his game” about a deceitful hunter, or “I went down to the walnut garden,” meaning that nothing inside it is repulsive. And likewise several interpretations of verses by commentators that, even though I think they are incorrect interpretations, I still remember the idea contained in them through remembering the verse (for example Malbim on Job 34:18–19, Proverbs 18:9, and Radak on Psalms 69:27 regarding consequentialism).