Your config file is working but not perfectly with GR (for me) :/
The game is using the resolution of the config file but GR fails while hosting.
I think GR doesn't get these resolution settings and its macro for launching the game and automatically host the room are not calculated with these new res.
So, the cursor is not positionning on "multiplayer" button that's why GR never finishes the "game hosting procedure" and then, other players who are "waiting for host" will never see their game launched.
I hope I'm alone in this case.
The best defence is attack!