ὅπερ δέ—the rel. clause qualifies παυόμενοι, for which we might have had ποιοῦντες.
λόγου τελευτᾶν—epexegetic of ὅπερ. The gen. with τελευτᾶν again in c. 104. If you ‘begin’ with a gen., you may naturally ‘end’ with one.
ἐς τὰ αὐτὰ καταστήσαντας—i.e. as we were before we capitulated.
τὸν ξυντυχόντα—‘any that comes’; cf. ό τυχών.