I haven't done anything with the dashboard yet, and I'm not sure what would be helpful to have there that is not already under the other 'my business' sections.
Also, as you mentioned, the administrator pages for uc_affiliate only show summaries of the visits and new users -- they do not show any of the sales information, which is only available through the user profile pages.
It would be excellent to have a French translation. I'll include a translation template in a future release.
Just to clarify, uc_affiliate does not use separate Drupal installations/databases, but a single installation set up for multi-sites (see: http://drupal.org/getting-started/5/install/multi-site). Since Drupal will use the default site directory for any hostnames not matched by other site directories, it can handle new subdomains without a new installation. (Your DNS must be set up to handle wildcard domains so that john.mysite.com is handled by the same server/account as www.mysite.com.)
Thanks for setting up a module contrib page for this.