καὶ ἃ νυνδὴ εἶπες πολλά τε καὶ καλά.
and many beautiful statements that you have said now
I do not understand how this clause is connected to the rest of the sentence. probably as dependent upon διαιρεῖς : καὶ γὰρ οὖν καὶ δεῖται τὸ ὑπὲρ Σιμωνίδου ἐπανόρθωμα τῆς σῆς μουσικῆς, ᾗ τό τε βούλεσθαι καὶ ἐπιθυμεῖν διαιρεῖς ὡς οὐ ταὐτὸν ὄν, καὶ πολλά τε καὶ καλά ἃ νυνδὴ εἶπες