Without the +set fs_game "MBII" command It runs
This is not how it works.
This command line argument is required.
I try to load the mod ingame
This is not how it works.
Do not try loading Movie Battles from in-game menu, the best that may happen is running with glitches
With the command I get the error in the attached image.
Do not try launching single-player; when you're asked, pick multiplayer.
Movie Battles is a multiplayer mod. It has no singleplayer (except from tutorial).
If you already trying running multiplayer, close MBII Launcher completely, from tray, go to Steam Jedi Academy properties, and click "Verify files".
You can also switch to MBII Client in MBII Launcher's settings.
This is the easiest way to play Movie Battles in your case.
And finally, clear "autoexec.cfg" file in order to get rid of "devmapall" error.
Autoexec.cfg are located in "Jedi Academy\GameData\MBII", and in "Jedi Academy\GameData\base".