I think that there is no easy way to clean the whole system of your data at this stage.
Of course you could unmount the packages from the sitemap and deinstall the packages from the apm but in my experience that has never worked without errors. Maybe in some future version postgres will support a "restore-to-point-in-time". Something like that could help. But nothing like that is available now.
But after the next new install you can immediately create a dump of the db and save that. Then you will be able to step back to this "after-install-condition" any time.
