Alter Poll Settings?

I am wanting to alter a number of things associated with the Poll module that comes with the Core modules in Drupal.

I would like to restrict the Poll Duration field to be only '1 week' (no more and no less).

Also I would like to restrict if the user can set the poll status (closed or active).

Another 'luxary item' I'd like to add (if possible), I'd like to show the results in a circle graph (sometimes where it makes sense). I dunno if going about something like that is possible.

Thanks for your time.