I do have a suggestion.
Take the HTML you got from Word and load it into a text editor such as Notepad++ and clean up the mess Word left in and make it nice clean HTML code and then you can take your chapter headings and make them look like <h2>Chapter 2</h2> and you'll get a good ToC.
The problem s that when you save as a webpage from Word, you get one hell of a mess from Word. Take a look and you will see what I mean. It's not good code at all. It's a real mess. I've cleaned up my share of Word's mess and it can take a good while to do so.