1) Shut your trap. Don't try to impersonate a dictionary on two legs, ok? Applies to classes with students of any level higher than pre-intermediate. If that high. If a student stops abruptly mid-story just in order to ask, 'oh, I'm sorry, how d'you say "truck-driver/masticate/illegitimate" in English?'don't you dare answer. The point is not for you to prove your verbal prowess. It's not even for the student to gain new vocab. The point is to teach the poor sod to express themselves in English with just the vocabulary they've got. Simply because they will never have all the vocabulary they need. As depressing as it sounds.
2) Make them correct syntax mistakes even if you did understand their mangled sentence the first time around. Correct