The in-game refresh rate is irrelevant anyway: it won't have any effect on the actual fps you see. But you can set a framerate limit in the Nvidia Control Panel that should work in both fullscreen and windowed modes. Right-click on the desktop, select the CP, then Manage 3D Settings > Program Settings, choose ts3w.exe (disc or Steam install) or ts3.exe (Origin install), scroll down to Max Frame Rate, enter 144 as the limit, click OK, then Apply to save the change.
There's also a global setting for max frame rate if you want to set it for everything, including other games, at once.
For the screenshots in fullscreen mode, what method are you using to take them? I've noticed that my screenshots are very dark if I use the Windows snipping tool, and Printscreen might be similar. My in-game screenshots taken with C look fine though, as do Windows screenshots taken in windowed mode. I haven't experimented with the settings @Cororon mentioned, but they're definitely worth trying too.
