You mention having a desired max frame rate of 66 (probably not achievable at 3440 x 1440) however you are setting that limitation the sim is halving that because of the ultra wide being sort of seen as two monitors.
Setting a desired frame rate cap is better using the games settings, your refresh rate and a little math.
Turn off the nVidia frame cap, turn on the in game V-Sync and set it to 1/2 for 60FPS or (more likely to work) 1/3 for 40FPS.