You may need to create an alias for /script to point to /usr/local/apache/share/htdocs/multi if that is where you're storing your help.html file. Apache wouldn't know to go into the multi directory for anything unless there is an alias set up or the documentroot is pointed there and it doesn't appear to be.
Try moving the help.htm file to the /home/webmaster/public_html/script directory and see if your request to domain.net/script/help works then. If not, there may be something wrong with mod_mime not knowing what to do with .htm files.
You can set the multiviews on the /home/user/public_html rather than the /usr/local/apache/htdocs directory. Any directory under the public_html tree would then have multiviews enabled. Just create a 'script' directory under /home/user/public_html and copy the help.htm file to it.
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