Doug!
Did you find a solution? I’m having the exact same problems.
Have tried to import posts fr?n a blog at wordpress.com without the media and instead using the media tools plugin to import external images and set featured images. Seems to work by the status report, but when completed the posts still points to the old media files at wp.com and the previews are blurry.
Im stuck! Please let me know if you have found a way
the blog: https://www.martingrander.se/mobile
Martin