Dave,
To do what you want, you may have to make a few changes.
First, you can not have a video and audio in the same post by just using category podcasting. What I would do is setup a podcast channel for each of the audio podcasts and one for the Video. That way, you can make one post, put the audio in the audio podcast media URL area and put the video in the Video podcast episode box (there will be one for each of your channels.
As for the stats. The only thing is with having multi podcasts off one wordpress blog is you have to put the redirect URL in the podcast episode box manually for each stats account. Also, in the Services & Stats tab in powerpress, take out the redirect URL (leave it blank) If you don't, every podcast episode no matter what channel will have your redirect URL you put there. We are working on getting it so each channel will have it's own redirect but this will be in a future release of Powerpress.
If you change your current category feeds to a podcast channel, make sure you have your iTunes URL in the new channel and set the new feed URL in the itunes tab of your cateory podcasting area to the new feed. Itunes should pick that up in a short time (a few days). If it doesn't, then look at a 301 redirect (search this forum for how to do that)
Hope that helps!
happy podcasting!
-Mike