Thank you very much for your suggestion. After reading much valuable information on Sigil here and doing much hard work, my wife has successfully created the EPUB version for my book.
According to her discovery, the best way to build an ePub version is cleanning out all of the stupid MS Word html tags and build the ebook from a very clean html source with just <p></p> and minimum information. It is much easier to add more format, fonts, color, images... to the book if you start up with this clean minimal file, Ughhh