A belated answer to the question about the key of F.

Irish music used the key of F. I have a tape (or is it a CD?) of music by the Irish flautist John Skelton. One piece is played on a flute in the key of F, his grandfather's, which had been found in a potting shed.

I have the edition of 'O'Neill's Music of Ireland' which was published in 1905. I started counting the airs in flat keys, most of which are F or B-flat. I got bored at 61 and stopped.

I will say, however, that F is not going to be popular nowadays. When I'm doing up a tune for my friends, I will change it from F to G. The chords for guitar are easier to play in the key of G, and the flutes appreciate being a step higher. But that's a modern perspective.