1. In general, it is singular and uncountable, but the sentence you reference is correct. It is a formal and somewhat literary style. In everyday speech: Africa has a special place in my heart. 2. Many people have affection for your country. Yes, that is a good sentence.

Hi! Here the word "affections" is used to to refer to one of the things that the speaker likes/ is passionate about. The sentence means: "Africa has always been IN THE LIST OF/ONE OF the things I'm passionate about" Here's another example: Traveling is one of my loves. In this example you can see the word "love" which is uncountable being treated as a countable word because the sentence means: "Traveling is IN THE LIST OF/ONE OF the things I love."