@samuvk
You could also try the following:
- Create a .docx version of your book with MS Word or LibreOffice.
- Convert the .docx file with Calibe to an .epub book.
- Check your .epub file for errors with the Calibre error checker and the IDPF validator.
- If no errors were found, upload the .epub file to KDP.
If the file size isn't much smaller, open the image folder in Windows Explorer/Finder and post a screenshot that shows the file types and file sizes.
If they're rather large, it might be possible to reduce their file sizes with lossless/lossy compression.