FWIW, you may be better off exporting to EPUB, making any changes to the HTML and CSS and then converting the EPUB to MOBI using Calibre.
This URL produces an error message.
Can you clarify?
Copy and paste it.
Tried that, to no avail . . .
I eventually figured out that the appropriate part of your URL was:
The > &docId=1000234621 is superfluous, including the unwanted space