Reviving an old thread as OP is having the EXACT problem I am having and I have enlessly searched without a solution.
The widescreen fixer and other mods are more for HUD fixes. Everyone I have heard from including the guys at widescreen gaming forums state the game natively supports widescreen resolutions but the menu and HUD is poor.
My game is being maxed at a 1900 x 1200 solution both by the in-game menu and by the configuration utility in the game folder.
My nvidia surround is setup and working fine in all applications except ME3.