I agree that HTML is the best source file format these days for easy conversion to others.
Have you tried just saving the HTML file directly from inside Firefox?
I wouldn't go through KompoZer or any other WYSIWYG editor if I could possibly help it. In fact, the constantly trouble I had with KompoZer screwing up my HTML files was the reason I finally decided to ditch WYSIWYG editors altogether.
And the terribly quality of Word-generated HTML files is legendary.
If you really must use a Word Processor, I've found that
AbiWord tends to generate somewhat-decent HTML output for converting.
The issues with quotation marks and en/em-dashes is probably a matter of saving the file in the wrong character encoding. I would think that saving the HTML file through Firefox itself would keep it in its original encoding. I guess you could do it manually by looking at what encoding Firefox is using (under View>Character encoding while viewing the page), and then copy and paste the source code into a sophisticated text editor (NOT something like Notepad!... but maybe, e.g., Notepad++), and then make sure it saves it in the same encoding. (I don't really know what the good editors are for Windows or mac, since I use linux.) But I would hope Firefox would take care of that for you if you just File > Save Page As...
But if you're really interested in this stuff, learning the HTML/CSS yourself. The tutorials at
w3schools.com are quick, free, and probably thorough enough for your purposes.