First off, I want to say that this is one of the few times that I've seen an intelligent critique of Derrida from a non-"Continental" perspective. The usual reaction is a kind of righteous indignation to slogans like "il n'y a pas de hors-texte", a refusal to actually read his works, and blanket attacks on "deconstruction in general" that blame it for everything that's wrong with the world today. Your reading is much more respectful and thoughtful, and its refreshing to see that.

However, I don't agree with it. Derrida's rejection of a transcendental signified is not an inductive argument. . Derrida describes two different interpretations, both present in Lévi-Strauss, of the cticism of totalisation: 1) "totalisation can be judged to be impossible in the classic style: you therefore recall the emprical effort of a finite subject or discourse panting in vain after an infinite wealth it will never be able to master" (throughout the following, my translations; L'écriture et la différence p. 423). In this style of critique, we renounce totalisation because we realize after many attempts that it's all in vain, that we poor mortals can't achieve it because of the shortness of our lives, the weakness of our intelligence, etc. A longer-lived, smarter being could do it, but we can't because of our limitations. This is, I think, more or less the way you've presented Derrida; but he describes another style of critique as well: 2)

The impossibility for a linguist to record every utterance of a language before making any claims about its structure (ED 422, citing Lévi-Strauss's Le Cru et le Cuit) isn't due to the vast number of signs that we unfortunately can't examine one at a time because of our empirical limitations; it's due to the finite number of signs not being being tied to a transcendental signified, that is, (at least some) signs always signify other signs. There's always more signifying than there is to be signified (ED 423-4). In Lévi-Strauss, the recognition of the "supplementary character of the signifier" (ED 425) is the "sad, negative, nostalgic, guilty, Rousseau-ist face of the thought of the game" (ED 427); Lévi-Strauss understands the infinite substitutions, but wishes there could be a full presence, an "archaic and natural innocence" (ED 427). But this infinite substitution can also be affirmed, as in Nietzsche, as

This second interpretation "is no longer turned toward the origin, affirms the game and tries to pass beyond man and humanism; the name of man being the name of that being which, throughout the history of metaphysics or of onto-theology [...] has dreamed of full presence, the reassuring foundation, the origin and the end of the game." (ED 427).

Derrida doesn't choose the latter over the former (though it's easy to tell where his sympathies lie). Instead, "we must try first to think the common ground, and the differing/deferring [différance] of this irreductible difference" (ED 428). We can't take sides between these two non-totalisations until we understand how they differ.

So the point of the article is not to argue that there's no such thing as meaning or even that we should be skeptical about meaning, it's to contrast two attitudes we can take towards meaning in an age where totalisation is no longer viable. (Hegelianism is dead.) Derrida isn't telling us not to believe in the transcendental signified, he takes that for granted; he's trying to discuss (and to get us to discuss) how to live without it.

There are two misunderstandings here. 1) The point of the commentary leading up to "The centre is not the centre" is not a reductio ad absurdum, ie. deriving a contradiction from the premises to prove that at least one of them is false. He explains on page 410: "The concept of a centred structure--although it represents coherence itself, the condition of the episteme as philosophy or as science--is contradictorily coherent." It's not that the contradiction shows it to be false, it's simply that the concept is unstable, that philosophies based on this centred structure tend to fall apart; see De la grammatologie for an example of how this happens in Saussure, Lévi-Strauss, and Rousseau.

This is another example of what I was saying in the last post. Derrida is not trying to propose philosophical theses (philosophèmes) and provide evidence for them using other people's texts (Heidegger, Nietzsche, Freud, etc.). What he does is take other people's texts and find the points of tension (which sometimes, but not always, means contradictions) in them. The "centred structure" is a point of tension in the history of metaphysics (=philosophy=the West, for Derrida) taken as a giant text. As Derrida explains in the same paragraph as above, these points of tension indicate a desire and a fear (for certainty and of the game, respectively). A "deconstruction" of a text isn't a criticism of it or a claim to prove that it's false (what could it possibly mean to accuse Hegel of falsity?), it's a continuation of Nietzsche's "dramatic" method of asking what kind of will is speaking in philosophical texts.

2) The second misunderstanding is about the term 'transcendental signified'. Note that it's not a transcendent signified, to which we could oppose an 'immanent' one (though I'm not sure what that would mean). The sense of 'transcendental' here is based on Kant's: "I apply the term transcendental to all knowledge which is not so much occupied with objects as with the mode of our cognition of these objects" (from Introduction, section V of the CPR). The transcendental signified is just the centre of the centred structure, a signified that could not be substituted for, and whose absolute certainty would provide a foundation for all the rest. An example is the "affections of the soul" that for Aristotle are indicated by our words. (Today we would say 'mental states'.) The two basic forms of transcendental signified are the archè (origin) and telos (goal): moments of full presence and absolute certainty from which we've fallen away by an unfortunate accident (Rousseau) and that we will one day reach again (Hegel), the middle period of absence in which we live being justified by the past or future presence.