You can get faster response for PowerPress issues at the blubrry.com forums, forum.blubrry.com.
As you are finding out, custom post types is not easy, even your category feeds have different URLs.
PowerPress supports additional custom post types by utilizing PowerPress's "Podcast Channels" feature. go to powerpress settings, under advanced options, enable "podcast channels", then click save.
Now on the main left hand menu of WordPress, under PowerPress you should see "podcast channels". click in there, then create a new channel for your custom post type. When editing the channel, click the last tab "other" and there will be an option there to select your custom post type. One tip, go to the default podcast channel, go to that other tab, and select the default post type of type post.
The podcast channel will then provide you a unique podcast only feed that is URL friendly if you have permalinks enabled, something way better to use for podcasting than the custom post types query string type feed URL.