htmlhelp version of unicode docbook files

Hi,


In our documentation we use several unicode characters.
That was no problem until now, cause we only converted html-preview and
pdf - the used fonts displayed all the characters just fine.

But now we want to publish the html version as CHM.

Problem 1:
How do i find a character set that displays all characters we use. (or
if not possible: as many as possible) 
Is there a tool that outputs all character-sets containing a set of
unicode-chars?

Problem 2:
How can i ensure, that the chosen character set really displays all
characters correctly?
If i dont get errors like:
"Output character not available in this encoding (decimal 8211)"
-can i be sure, that all is fine? Or may some characters be corrupt?


Thx in advance,

Sebastian Fey