Do those commands work if you connect to the pi using ssh and then run them in the ssh terminal? If not then you need to sort out what commands you need. Once that works then try in an exec node.
i'm seem impossible to send easily the second vidéo on HDMI2 directly ...
only one thing works but is not perfect. I use terminal gnome and i move the vlc windows in X and Y, but when i launch a vidéo the terminal opening few second and launch the vidéo. For me is not possible.
With omx player it was very easy but with vlc is very difficult...
I don't find the solution to loop a single vidéo and i don't find the solution to play a vidéo on the second monitor... it's incredible...