1) In iTunes, Full Screen from the menus (or clicking on the square that's in the white pop-over controls inside the window) defaults to going full screen on the *main* display. In System Preferences -> Displays -> Arrangement, if you drag the menu bar in the picture from one screen to another, you can define which one is Main (the one that has the menubar on it in the Displays preferences is the one that will have the dock and the menubar on it in, and also the one iTunes will play full-screen on).
2) I can plug my TV in and check for you, but I think VLC, by default, will go full screen on whichever screen in which the movie is playing in windowed. I.E. if you drag the windowed movie onto the TV's display, and then go full screen, it'll show up over there.