This is a known issue, you can find more info here: https://github.com/gildas-lormeau/SingleFile/blob/master/faq.md. Although, with your level of requirement, you should save page in the WARC format. This is probably your only hope of saving the web page properly.

The purpose of SingleFile is to save the page in a single file in a standard, durable format - that's what the extension is all about.