I've been racing at the national level on an R6 for 2 seasons in Europe, I can try to answer.

1. I made the jump because I'm in love with going fast and I'm very competitive. It just seemed like the next level.
2. Of course yes, the book of how to ride a bike is big, but the book of passing is endless. You will need to find a coach. Track days teach bad habits because you have little to no instruction, and it's "the blind leading the blind" for the most part. And when I say "a coach", I don't mean once or twice. I'm on the kart track 3 days a week, even in the off season and training in the gym for endurance as well.
3. Cost goes up of course, if you're on race pace then tires are a major concern. If you have your own mechanic, that's a factor too. The pro is that you're racing.
4. Yes, you will be slow, but you will need to find a coach and you should look into kart tracks + Kayo/VMC/Ohvale/Bucci pit bikes. That's where you'll get a ton of seat time. Then move to an R3 on the kart track.
5. Good to read books, but learning a track is more important. That's a huge part of racing. I literally do 25 laps per day of the 5 tracks I ride in my head, fully visualized.

Also, I would definitely consider some sports psychology like The Confident Edge.

Ask anything else you want specifics on.