Earlier in this thread, baf posted the command line he used to do the conversion on the Mac here. This worked on my Mac.
https://www.mobileread.com/forums/sho...&postcount=338
Kindle Previewer 3.app typically installs in /Applications
Path to the bundled jre is here:
"/Applications/Kindle Previewer 3.app/Contents/lib/fc/jre/"
Path to where the jars are found is here:
"/Applications/Kindle Previewer 3.app/Contents/MacOS/lib/fc/lib/"
Let me know if you need more info.
KevinH