Try:
PrintPrint > Uncheck the option "Rewrap contents to fit page" Rewrap contents to fit page > PDFPDF > Save to desired location
This seems to retain the original formatting. As far as background goes, I doubt it is an option to natively export a dark mode themed-themed PDF as printing such a page would be a massive waste of ink. You would have to screenshot your note and print the screenshot to save the dark formatting.
Standard screenshot: CMD + Shift + 3 Cmd+Shift+3