τυχών κεν ... σχέθοι = εἰ τύχοι, σχέθοι κεν. Similar positions of ἄν are common enough in prose. Here the opt. with κεν is an imperative.
ἁρπαλέαν = ὡς ἁρπαλέον τι. “With eager clutch.” Compare P. 8.65: ἁρπαλέαν δόσιν.
πὰρ ποδός: Cf. P. 3.60: γνόντα τὸ πὰρ ποδός, and I. 7 (8), 13: τὸ δὲ πρὸ ποδὸς ἄρειον αἰεὶ σκοπεῖν.