You have managed to get the Store to recognize the Feedburner version of your feed and things are now looking a bit better. The overall entry for the podcast, and each episode, have their own 'itunes subtitle' and 'itunes:summary' tags. When you set up an episode there should be somewhere you can enter the data for these so that you can have individual entries for each episode.
The 'itunes:subtitle' appears in the line with the episode and should be kept to a few words or it will be truncated. the 'itunes:summary' appears when you click the 'i' button which appears when you select an episode. This can be much longer, but don't include any html. You can have paragraph returns, but keep to plain text or things will look messy. Don't use an ampersand ('&') as it causes problems - if you want to have one, substitute the code
&
Otherwise avoid odd characters, in particular don't copy in 'curly quotes' from a word processing document.