Rather than DESTROY your books.
Reduce the size of the covers that get embedded.
Use the
Resize Cover Plugin: Then
Embed the new metadata: Then Send the book (again) to your device. AFAIK, as long as the
Send Template remains the same, the book is just updated (replaced) and the notes and stuff remain .
OBVIOUSLY TEST THIS on some book you don't care if the notes are lost.
OTOH if you choose to destroy, Bret gave you the REGEX to remove ALL images from CONVERSIONS. THERE IS NOTHING that Calibre has to fix directly, books on the device. Convert/Edit then replace (with all the ramifications of that upon annotations)
Seriously: You need to do some housekeeping on that device.