I'm not sure about every region, but FF> REW<< and Pause are not supported with DLNA, and in the U.S. models, this is stated i the manual.
Subtitles have to be part of the container, and this may require encoding the file.
If you'd like to check on an upgrade, I'd recommend contacting the Samsung customer service center in your region.
I have just bought this TV.
The streaming of video from my NAS server works, but it is not possible to set subtitles on. Furthermore, the mediaplayer in Samsung TV works lige the first generation of media players! The Reverse and forward function is not working with the remote control keys and the advance to the next chapter does not work too.
Is there any kind of upgrade for the media player which could modernise the functions?