To pause playback, touch the BlackBerry screen. This will display a screen with a 'Resume' button. (new as of Version 12 of the BlackBerry app)
Flix doesn't yet support rewind or fast forward. While I hope to improve this situation, a workaround if you need to jump to a particular part of the movie is to start the movie, and then on your PC, right click the Flix tray icon (bottom right corner of the screen, and you'll likely need to click the little "up arrow" to see it), and select "Show Movie on PC Screen When Playing". A window should open showing the movie playing. Use the player controls to jump to the desired part of the movie. After waiting 10-20 seconds for the buffer to refresh, the video playback on the BlackBerry should sync to the appropriate location.