Would you be kind enough to tell me whether I am right with my interpretation of the expressions in bold in the following sentences?
Over the last five years, this plant, like the U.S. steel industry as a whole, saw its profits soar. By mid-2008 Nucor had hit an all-time high. But then things changed, overnight.
overnight = during or for the length of one night
You're right that overnight generally means in the timespan of the night, but in this case it means very quickly. Probably not in 12 hours.
If there was an explosion or fire which destroyed the plant, then yes, it would be in the span of one night.
And when he said a few plain truths about Mr. Lloyd George at meal-times, or made the slightest attempt to raise the tone of the table-talk above the level of the silliest persiflage, their attention wandered ostentatiously. ostentatiously = characterized by or given to ostentation; pretentious
You have the correct meaning of ostentationsly, but it doesn't apply to the sentence. I would use immediately, quickly, noticably.
He wanted badly to get away from his family to some place where he could think of its various members with quiet pride and affection, and otherwise not be disturbed by them....
The use of badly with want was once considered incorrect but is now entirely acceptable: We wanted badly to go to the beach.
• The adverb badly is often used after verbs such as feel, as in I felt badly about the whole affair.
badly = very much; greatly
The private party was lavish; the entertainment [was] top notch.
top-notch = first-rate; excellent, exceptionally good of its kind
Thank you for your efforts.
I am not a teacher.