Is it audio only, no video? That doesn't work in Silverlight player. I'm not sure about the sub-titles but Wowza's recently added Closed Caption features do not include smooth streaming and Silverlight player
I don't think so. I assume you are playing the ism file with the smil prefix. Wowza supports an audio only rendition for iOS, but not for Silverlight.
If you have ismv files with multiple bitrate renditions encoded into one file (use Expression 4 Encoder), that is not supported in Wowza. You have to have separate files.
Also note that the ismv files are fragmented, which Wowza can stream, but it is higher overhead especially at the start of playback. We recommend the encoding path using Expression 4 Encoder that is shown in this article: