A few more tiny quibbles:
1. 'But in his own wisdom…' is rather ambiguous if you read only the English. I suggest 'specialty' or 'area' or 'domain' or something less literal to render σοφός in that sentence.
2. Perhaps you could smoothen out the syntax of 'I could list off many others, who, good though they were, couldn't make anyone else better, relative or stranger.'
3. 'When I look at it from this point of view, Protagoras' can't be right for εἰς ταῦτα ἀποβλέπων. There's no point of view as such mentioned in the previous lines; rather, Socrates is drawing an inductive inference from his *examples* about the teachability of virtue, which is what the pronoun must refer to. I suggest: 'When we keep these in mind, Protagoras', or better, 'Given all this, Protagoras…' Also, do you think you should do something with the οὖν there?
4. Any reason you alternate between 'show' and 'prove' for ἐπιδεῖξαι and cognates?
5. I have a few questions about word choices in Protagoras' speech, but I take it you want him to sound a little bit affected?