When you run that epub through Amazon's KindlePreviewer it turns it into a .mobi file. Unless something's changed recently they do accept .mobi files since that's the way I did my first two.
And relax on this. I've found formatting to be a bigger challenge than writing. These days I've got it figured out but on my first book I had more than one migraine while trying to turn it into a eBook!
TL
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