Having worked in the music department for 20 years, from 1986 to 2006, I can say that all of your responses are correct and show excellent deductive skills.
The only thing I can add is to reinforce that David Splane is the game changer. His approach was well received among the music people, as we had been clamoring for music to play a more prominent role as an emotional vehicle for some time. Other factors are that one of the professional arrangers used on occasion suggested adding new songs to see what the reaction would be. Any song that was a "hit" with the r&f would be considered for inclusion in the next book. The lead musician has long been of the opinion that group singing has always been a healthy pastime, and although not practiced as much in modern times, should be revived.
What have always stifled the creativity and quality a number of the musicians are capable of, are the restrictions imposed by and musical taste of the GB. So long as the GB signs off on the finished product, you are going to have uninspiring, poor-quality music.
As far as connecting with young people, I think the Pew studies show how effective JWs are with this. Kind of like the way George Burns described having sex as a 90-plus-year-old: "It's like shooting pool with a rope."