A. Use "an" before vowel sounds except long "u" and before words that start with a silent "h." It should be "a university" and "a historical place."
The apostrophe in the following sentence is correct: The Joneses' flat is too small. "Joneses" is the plural, and it is correct to form the possessive of a plural ending in "s" by adding an apostrophe.
I have heard the expression "in the pink of health." I think it's all right.