Nice tutorial!

KDP has gotten a lot easier, so now that you've mastered Medium, it might be time to try Amazon.

I suggest you try Draft2Digital's free services to start. It's free to convert your book from Word to Kindle (and all the other ebook platforms) in their dashboard. Once you've uploaded and converted you can see if it looks good enough to publish on Kindle, etc.

I suggest uploading the D2D epub file to KDP yourself, but if you want to publish everywhere, you can use D2D for the rest. They just take a small percentage of each sale.

Please reach out if you need more specifics. I've done dozens of books through KDP and D2D!

Roland