The 'automatic downloads' page that you posted from only applies to future purchases i.e. if it's turned 'on' on your iPod, then if you now purchase a song on your iPad then it should also download on your iPod.
Depending upon what country that you are in then you might be able to re-download your iTunes purchased music via the Purchased tab in the iTunes store app on your iPod : re-downloading. For non-iTunes purchased and/or if you can't re-download it then you will need to sync via your computer's iTunes (you can't connect an iPod to an iPad for direct transfer). If you don't have your iTunes purchases on your computer's iTunes then you should be able to copy them over via File > Transfer Purchases (File > Devices > Transfer Purchases on iTunes 11)