How to repair broken simplecast RSS feed?
see above example.

The original feed contains no episode-specific entry URL behind its title.
The feed reader (also five filters) instead interprets the URL to the mp3 podcast file as entry URL, but also this comes wrongly formatted.

example for the output

This is how it should look like

or else like this:

How do i either repair the mp3 URL?
…or else: how do i create an own feed based on the episode page?

Interesting. As you say there’s no HTML page associated with the items for Full-Text RSS to retrieve text from. Perhaps we should generate HTML for an embedded player using the enclosure URL (pointing to the MP3).