I need to give a client access to his AWStats, but I don’t want to give him the FTP login and password currently used to access the stats. Can a different username/pw be set up to just view the AWStats?
If I remember this correctly 
log into H Sphere > click on Stats > click on magnified glass (under Webalizer) for stats
The page that opens up (in a new browser window) will have your stats and you can email the URL of the link to your customer for them to view the stats without having to login to H Sphere 
Hope this helps
EDIT: just realized you want AWstats 
The way awstats runs it runs the perl as the logged in user, I don’t think it will work any other way 