I listen to online radio show about homebrewing and beer from The Brewing Network
http://www.thebrewingnetwork.com/They do basically what you're looking to do...live streamed shows a couple times a week with past shows archived as podcasts available via iTunes.
I'm not sure you're going to find 1 provider that can do everything you're looking for because it's pretty specific. I know the brewing network at least used to use abacast as their streaming provider
http://www.abacast.com/but serving up web pages, creating mp3s of the shows and hosting the shows for iTunes are all outside the scope of the streaming service AFAIK.