Feedburner seems to work fine for most people - a few years back it was liable to cause problems, and the advice then was to avoid it, but I've seen no complaints recently.
If you want to revert to the original feed you can do this without too much difficulty. You can't use a 301 redirect on someone else's server, and you don't want to get into re-submitting.
Follow the instructions on this page:
Place the 'itunes:new-feed-url' tag in the original feed: Feedburner should pick it up, then iTunes will see it and change to the original feed. The tag will still be there, of course, but as it will now be redirecting to itself it won't do any harm, and you can remove it after a couple of weeks.
My link above includes instructions for checking what feed iTunes is using, and you should do this to make sure that it has indeed changed. The Store page may take a couple of days to update.
I'm not sure I understand when you say in your instructions, "add the following tag to the top section of the feed, between the 'channel' tag and the first 'item' tag." What is the channel tag? What is the item tag?
I put my new feed address in the middle of the iTunes words below. Does this look correct?
If I just stick this in the original feed and save, should it update iTunes or am I missing something? Will iTunes eventually show my feed just as:
The tag is correct. It has to go in the feed, in the top section before you come to the information for the top episode (the first 'item' tag). As you are creating your podcast in WordPress you will probably have to do it there - I don't know whether it allows you direct access to the feed to edit it, but there may be somewhere you can add this information. I'm afraid I can't advise on WordPress.