πάντα τὰ αὑτοῦ: “all the powers of the body and soul.” Cf. the passage quoted below (10), and Crito 46 b τὰ ἐμά. The construction of καὶ πάντα κτἑ. shows another example of the common Greek idiom of following a rel. by a demonstrative. See on 452 d.
εἰς τοῦτο: takes up again οὗτος ὁ σκόπος for the purpose of recapitulating in its correlative clause, ὅπως κτἑ., the substance of what has been explained; οὕτω again reiterates in one word the whole previous participial clause, and connects it with πράττειν, which has the same construction as ζῆν. The positive directions summarized in οὕτω are still further fixed (after Plato's habit) by the following negative direction in the epexegetical participial clause οὐκ ἐπιθυμίας ἐῶντα . . . πληροῦν. After πληροῦν we find the parenthetical criticism ἀνήνυτον κακόν, while the life of the man who attempts what is deprecated in the participial clause, is characterized very emphatically by the appositional tag which completes this rambling, intensely conversational sentence.
συντείνοντα: the image is that of drawing the bow and aiming, to the employment of which, σκόπος has led the way. We find in Rep. ix. 591 c the same image in a similar connexion, ὅ γε νοῦν ἔχων πάντα τὰ αὑτοῦ εἰς τοῦτο ξυντείνας βίωσεται.