I McPherran 1996, 194-208 does a good job of criticizing reductive readings of the divine sign, though he does not emphasize the political significance of the daimonion.
2 Pangle 1987, 1-20 provides a helpful restatement of Grote's case for the authenticity of these dialogues. This is not the occasion for defending these positions. Let me note only that what arguments there are against their authenticity depend wholly on internal criteria. That is, many scholars judge the contents of Theag. and Ale. to be so unlike other Platonic dialogues that they must be forgeries. The best way to combat such an argument is to bring out continuities, which I will try to do. But even a reader who thinks these dialogues are not by Plato may still think that they are interesting and penetrating reflections on Socrates and his relationships to politically ambitious young men. 3 Momigliano 1993/1971, 46 has given the classic statement of this alternative to Vlastos: "Biography acquired a new meaning when the Socratics moved to that zone between truth and fiction which is so bewildering to the professional historian. We shall not understand what biography was in the fourth century if we do not recognize that it came to occupy an ambiguous position between fact and imagination. Let us be in no doubt. With a man like Plato, and even with a smaller but by no means simpler man like Xenophon, this is a consciously chosen ambiguity. The Socratics experimented in biography, and the experiments were directed towards capturing the potentialities rather than the realities of individual lives. Socrates ... was not so much the real Socrates as the potential Socrates." Kahn 1996, 1-70 does a thorough job of exposing the implausible philological assumptions behind the Vlastos paradigm. I believe his conclusions also support a much more sympathetic approach to Xenophon than is common, though as far as I can tell, Kahn does not share this belief.
4 Pangle 1987, 154n3 suggests that Theages is rather stupid, and says that this passage does not ascribe to him a philosophic nature. I do not see how Pangle would explain what Socrates means by saying that Theages has "all the other resources that contribute to banishment from philosophy."
5 Memorabilia 4.2.11 shows Socrates eliciting the desire for kingship, but the extension to the barbarians is not part of Socrates' seduction of Euthydemus. It is part of his approach to Glaucon (Memorabilia 3.6.2-3, quoted above). Both the erotic context and the extension of ambition to the barbarians are present to some extent in the Meno. Socrates describes himself as unable to resist Meno's youthful beauty (76b4-c2), and because of this develops a definition of virtue that Meno finds congenial, and that culminates by pointing out Meno's connections in Persia (78d1-3).
6 The Protagoras also figures Socrates as the guide of young Hippocrates, and perhaps of Socrates' beloved Alcibiades, to the sophists' underworld (315b9 and c8).
Kahn, C. 1996. Plato and the Socratic Dialogue. Cambridge, UK.
McPherran, M. 1996. The Religion of Socrates. University Park, PA.
Momigliano, A. 1993/1971. The Development of Greek Biography. 2nd ed. Cambridge, MA.
Pangle, T. 1987. The Roots of Platonic Political Philosophy. Ithaca, NY.