having trouble changing feed URL in Wordpress

From your post it looks as if you have added the tag but removed all the other episodes: is this in fact what you did? - as the actual feed hasn't currently been modified I can't tell.

The redirect isn't anything like immediate: you need to add the tag to the complete feed and leave it until iTunes has moved to the new feed, which can tak a couple of weeks. You can tell when this has happened by subscribing anew from the Store page and clicking the 'i' button at the right-hand end of the top line in the 'Podcasts' page in iTunes.

Incidentally, the tag itself is correct but shows as if there is a line break before the closing tag - this is probably just the way my browser displays it (small screen - netbook) but check that there isn't a line return in there.

I have now confirmed that there is a line break in your tag, and you should remove it.

A further complication: you give your current feed URL as
http://bethanypodcasts1.wordpress.com/feed/

However the feed that iTunes is using is
http://feeds.feedburner.com/BethanyPodcasts1

Possibly the former is a feed that you submitted to Feedburner, and then submitted to iTunes from Feedburner - the content is the same but there are differences in the coding as Feedburner adds tags for Atom etc.

I don't know whether , if you add the new-feed-URL to the original feed, Feedburner will pass it on. You can only try. You should add just the new-feed-url tag as you have listed it (without the line break) into the top section of the feed, after the title and before the first 'item' tag, and re-upload it. Nothing will happen immediately, but if you like to post when you have done it I will have a look at it.

I'm not familiar with Wordpress, but a lot of programs and online services prevent you accessing the code, presumably to prevent you from mucking it up, but it can make things difficult.