Here is my response:
I think you have a fine analysis of The Protagoras using a philosophical standpoint.
Some helpful observations on this concept (including reference back to Aristotle's points about the same; I noticed your point similar to Aristotle on page 3 of the essay - people do what they think will make them happy; the problem is in learning where true happiness resides and habituating ourselves to it; the Nichomachean Ethics.)
Here is the Greek in context:
εἰ ἄρα, ἔφην ἐγώ, τὸ ἡδὺ ἀγαθόν ἐστιν, οὐδεὶς οὔτε εἰδὼς οὔτε οἰόμενος ἄλλα βελτίω εἶναι ἢ ἃ ποιεῖ, καὶ δυνατά, ἔπειτα ποιεῖ ταῦτα, ἐξὸν τὰ βελτίω: οὐδὲ τὸ ἥττω εἶναι αὑτοῦ ἄλλο τι τοῦτ᾽ ἐστὶν ἢ ἀμαθία, οὐδὲ κρείττω ἑαυτοῦ ἄλλο τι ἢ σοφία.
Then if, I proceeded, the pleasant is good, no one who has knowledge or thought of other actions as better than those he is doing, and as possible, will do as he proposes if he is free to do the better ones; and this yielding to oneself is nothing but ignorance, and mastery of1 oneself is as certainly wisdom.
- from Perseus project (http://www.perseus.tufts.edu/hopper/text.jsp?doc=Perseus%3Atext%3A1999.01.0177%3Atext%3DProt.%3Asection%3D358c).
Some few thoughts of my own on this dialogue (which, thank you, I am intrigued enough to go back and read a second time now).
1. note that from the start Plato is setting up a series of dual figures; a bad (or false) and a good (or true). First Socrates and "the friend" who open the dialogue, then Socrates' comment about leaving Alkibiades (the true love) for Protagoras (the false love), which is ironic b/c Alkibiades is also the false man (loved only for appearance) whereas Protagoras is jokingly held up as the true man (loved for his mind/soul/nous); then the slave makes way for Socrates at The Friend's bidding; then Socrates mentions that his conversation with Hippocrates occurs in the morning (btwn the false dark ignorance of night and the dawning truth of daylight); then there is the analysis of what sophism is in comparison with philosophy (as a false act of knowledge for personal gain compared to a true act of knowledge for love), also the seeking out by Hippocrates of Socrates as the true "doctor of the soul" compared to the contingent journey to Protagoras as a false "doctor of the soul" and then the discussion between the two in which the true doctor trounces the false. Seems that the factors that from the beginning are being established are false vs. true, ignorance vs. knowledge, selfish vs. selfless , lack of love vs. love. Thus the opening "chords" of this little rondo by Plato seem to concern a comparison btwn a false path of life and a true.
2. taken in the larger context of the Platonic corpus, this dialogue seems to be a repetition of that thesis that the vision of the good is an overpowering vision that prompts a man to transcend the pettiness of selfish desire and thus become master of himself (autonomous).
3. seen in the light of the literary context and the overall corpus, it would seem that the discussion of akrasia has to be fitted into the larger discussion of incontinence or inability to rule (akrates) and the power to rule (krates). Plato is offering a philosophical distinction which does indeed set philosophy buffs panting, but really it is more of a theological work.
Drawing, then, from Michael Davis' most excellent article on the death dialogues (Wonderlust:
When you buy victuals and liquors you can carry them off from the dealer or merchant in separate vessels, and before you take them into your body by drinking or eating you can lay them in your house and take the advice of an expert whom you can call in, as to what is fit to eat or drink and what is not, and how much you should take and when; so that in this purchase the risk is not serious. But you cannot carry away doctrines in a separate vessel: you are compelled, when you have handed over the price, to take the doctrine in your very soul by learning it, and so to depart either an injured or a benefited man.
For Socrates in this small triage on the soul of Hippocrates the doctrines matter; to set a man on the right course of action away from the false course of action is an imperative. Thus to the passage on akrasia: the "other possible course of action". Here the impotence, or incontinence of the present life or actions (ποιεῖ) of weakness are held in comparison to the stronger (δυνατά), better (βελτίω) way which is fostered by true wisdom (σοφία). Here's the ultimate point: Socrates' "new way" of action is one which acknowledges the darkness and meaninglessness of our existence but also recognizes that living in that meaninglessness (whether as a nihilist or as a sophist) emasculates a person and makes them incapable of acting. Aquinas also seems to recognize this, that the abyss is a reality but discussion of it is bootless and only makes one incapable of acting. Only adherence to the seemingly paltry and rather shabby doctor, Socrates, offers a resurrection of thought, like the dawn breaking, that can trounce these sowers of sorrow and addiction and offer the real autonomous rule that provides a counter to the horror of death.