Hayley,
In your case, I would say you should change the setting back to "summary" in the reading settings, and then in the PowerPress settings > Episodes tab, enable iTunes summary. Then in your post there will be a box where you paste in exactly what you want to show in the feed.
Also, note that iTunes, Apple Podcasts and all other apps, can show what they want as far as how much of your show notes. So the full text may never show up completely depending on how the apps are setup.
Email me mike@blubrry.com if you want a more geeky answer as to why to set reading back to summary.
Of course, give iTunes and everywhere else a bit of time to get the changes if you change something. Email me your feed address if you want me to check it for you.
Hope this helps!