If you're comfortable with (carefully) editing the fsall/settings.ini file, there's a graphics section where you can edit some graphics settings, including:
[GRAPHICS] FullScreen = yes ; Full screen window XScreenRes = 1920 ; Screen width YScreenRes = 1080 ; Screen Height
(When you're using FullScreen, you should use a standard resolution supported by your monitor.)
And you can use this line
Adapter = 1
to pick which monitor to use (starting at 0).