ἐπὶ τούτοις—in conseqnence.
πέμπει—asyndeton after a demonstrative is fairly common.
ἐξ ὅσου = ἐς τοσοῦτον ἐξ ὅσου, the antecedent being omitted as in Plat. Phaedo 78B ὅθεν ἀπελίπομεν ἐπανέλθωμεν, and often with relative adverbs.
διάγγελοι—one would have thought that it was high time for even Nicias to be somewhat sceptical. Moreover he had played a similar trick on the Syr. early in 414 It is strange too that any man who had appeared in the δικαστήρια should not have understood the art of lying. But their sufferings prob. unnerved the A. for the time.