Podtrac is a stats tracking service. Did you ever sign up with them? That's the only way I can think of that any of your feeds would be using a Podtrac URL. If you have used Podtrac before, and you have a Podtrac account, you can see if they can redirect the feed to the feed URL you'd like to use. Alternatively, you could contact iTunes Support and ask them to update your listing in the iTunes Store with the feed URL you'd prefer.
I'm not sure why you're having that issue with the PowerPress subscribe links. I am checking with the rest of the support team to see if they have any ideas. Also, PowerPress 6.2 was just released so make sure you're updated to the latest version.