I would approach this a bit differently.
Personally I would use JSON feeds which provide all of the available data.
Now if you want to create a new view which produces RSS, I would copy /view.feed.php and create the view based on that.
The ordering is set by the params in the settings.
// Set ordering
if ($params->get('singleCatOrdering'))
{
$ordering = $params->get('singleCatOrdering');
}
else
{
$ordering = $params->get('catOrdering');
}
This is the ordering for the category, depending on the case, the ordering is set differently.
