Probably I'm missing something, but looks like it's not possible to change date format in your extensions. This is due to lack of $format value in get_localized_date() function calls:

get_localized_date($item->created)

It always gives date in YYYY-MM-DD format, which mostly used in US and not very good for other countries. I thing it's much better to replace this code with:

get_localized_date($item->created, JText::_('DATE_FORMAT_LC'))

Maybe it's not global and you've just missed some places. For example, My Questions list template has this issue.