προτιμῶν, ‘that you value.’ προτιμᾶν generally means to ‘prefer’, followed by a genitive of the thing compared.
ὥστε πιστοτέρους εἶναι τοὺς σοὺς λόγους κτἑ: cp. Paneg. 81, where Isocrates describes the ancient Athenians as πιστοτέροις τοῖς λόγοις ἢ νῦν τοῖς ὅρκοις χρώμενοι.
τὰ συμβόλαια, ‘contracts.’ συμβόλαιον is lit. a ‘token’, so ‘signature’, esp. of a ‘bond’ or ‘covenant’.
νόμιμον: here used in the rare sense of ‘law-abiding’; cp. Antiph˙ Tetral. A. β, 12 (p. 117) φιλοθύτην δὲ καὶ νόμιμον ὄντα.
περὶ πλείστου δὲ ποιοῦ κτἑ: for the sentiment cp. the praise bestowed on the ancient Romans by Sallust (Cat. 6), because “magis dandis quam accipiendis beneficiis amicitias parabant.”
