Another possibility to check out is using the Kindle Previewer (free download from Amazon) to convert your epub and then sideload it to your Kindle apps. See
Kindle Previewer for the download. It does a decent job of displaying what your ebook will look on like Kindle e-Ink or the Kindle app on phones or tablets. One item to remember is that selecting a .mobi output file will generate a dual format file with .mobi and .azw3/KF8 files embedded.