You know you can run two instances of maptool on the same computer? Or is it a mouse/keyboard thing?
Just start it a second time. Set up a server with one instance as GM. In the other maptool instance join the server as player (probably best to use the direct connect option). Then one will always show the player view and you get the GM window all to yourself.
Put the player instance on the second monitor, point it at the players and you are good to go.