I looked at your test feed and there is an error which may be the cause of the trouble. Your 'enclosure' tag reads
<enclosure url="http://wippermann.net/Download/Wip%20-%20Balearic%20Beats%20II.mp3" length="74822240" type="audio/mp3" />
The 'type' attribute is incorrect. It should read type="audio/mpeg" and this might be enough to upset iTunes. This applies to the entries in your full feed. So the first thing to do is to correct that and see whether it solves the problem.
If it doesn't there are other oddities to investigate. The audio file in the test feed plays in a browser but iTunes will not download it. The feed appears to be OK when looked at in Firefox (my default RSS reader) but using curl in Terminal (which should display the entire contents) I get:
curl http://wippermann.net/WGHPodcast/WGHTest.xml
<html><head><title>Request Rejected</title></head><body>The requested URL was rejected. If you think this is an error, please contact the webmaster. <br><br>Your support ID is: 15793630651847968699</body></html
This is an error page generated by the server so the ID number it quotes should be included when you contact the people running your server.
None of this makes a great deal of sense, since the problem in iTunes isn't with the feed but with the media file. When testing that for byte-range requests in Terminal I get:
curl -I -r 200-300 http://wippermann.net/Download/Wip%20-%20Balearic%20Beats%20II.mp3
HTTP/1.1 200 OK
Connection: close
Cache-Control: no-cache
Content-Type: text/html; charset=utf-8
Pragma: no-cache
Content-Length: 211
This at least indicates that the server is apparently not responding to a byte range request - the expected result would look like this:
curl -I -r 200-300 http://rfwilmut.net/podcasts/Soundof78s36.mp3
HTTP/1.1 206 Partial Content
Date: Sun, 29 Nov 2015 10:50:01 GMT
Server: Apache/2.4.12
Last-Modified: Sat, 20 Jun 2015 15:27:15 GMT
ETag: "57a161d-a3939a-518f4acea0eb7"
Accept-Ranges: bytes
Content-Length: 101
Content-Range: bytes 200-300/10720154
Content-Type: audio/mpeg
I don't know what else the report on your file indicates, except that I would be suspicious of 'Connection: close'.