You should only do one of these two things:
A.) Create a podcast feed on your own site, using the PowerPress plugin, where you add your LibSyn media file links to your Podcast Episodes on your own site (what we recommend)
B.) Use the LibSyn-generated feed
There's no way to sync the two feeds automatically, so you're making a lot of extra work for yourself by trying to create them both. Pick the one you feel suits you best and go from there.