It's not clear what you've been up to. You say you changed the feed 'unknowingly'... there is a distinct procedure for telling the Store to use a different feed. If you changed the feed and didn't follow this the Store would stick with the old URL and if there was nothing there your podcast would freeze as of the last time the feed worked and would eventually be removed. That doesn't appear to be the case, particularly as there is the extra episode which isn't in the current feed.
The only way I can see duplicates arising is if when you changed the feed you also changed the 'guid' tags. This would make all the episodes look like new ones, though this would only affect iTunes subscribers who had already downloaded episodes. I don't know how this would work on an iPhone, as I say I don't have one and I'm not familiar with the podcasts app. Probably someone who is will be able to chip in.
Podcast analytics are only available by login with your Apple ID.