Wow, each question is so thought-provoking that you could write a book! In this comment, I’ll just try share some of my thoughts on question 1. 

1. While studying so-called “minor” languages (such as Hebrew or Català) can be immensely rewarding, Cantonese is in fact a major world language. According to the data from Ethnologue (2019, 22nd edition) as shown in the relevant Wikipedia article, Cantonese has 73 million L1 speakers. This number compares favorably with such famous languages as French (77 million), Egyptian Arabic (65 million), and Persian (all dialects: 62 million). While Cantonese may not be the official language in any sovereign country, it has millions of native speakers around the entire planet, and is still the most spoken variety of Chinese in the Western Hemisphere — the same hemisphere where I happen to live.

2. Cantonese gives you more of what you study Chinese for: More tones, more fun characters… and words that are just M or Ng and a tone. Isn’t that what Chinese is all about?

3. Historical linguistics. As a bit of a language nerd, I appreciate the fact that Cantonese pronunciation is more conservative than Mandarin. This is particularly true with the tones and the finals, which together constitute the rhyme. Naturally, this is ideal for reading Tang poetry out loud. Also, Canto-pop is famous for matching the lexical tone to the melody, which is really cool. Additionally, Cantonese has avoided the merger (before front vowels) of g k h with z c s into Modern Mandarin j q x.