Hey there, I recently faced a similar problem where I wanted to manage my highlights, even potentially put them into quotes apps so it would help me remember them, or just be able to get a nice condensed list of all my quotes for each book on my Kindle.
This doesn't answer either of your questions, but another way you can retrieve all the highlights from your Kindle could be to use a free tool that I recently created where you can convert your My Clippings.txt into an Excel CSV which contains all your quotes in a nicely presented format.
You can give it a go here - hopefully it helps
https://kindle.brendantrinh.com/