About that 50 Hz bug - are you sure your game is really running in DX9 mode? Check r_DisplayInfo 1. You have to add the "-dx9" parameter to the shortcut you use to launch Crysis if you want to start the game in DX9 mode. It uses DX10 mode by default, which is known to be broken in some ways.
About that Very High settings bug - can you explain it a little bit more? Maybe it's some new bug but i think it's some strange error caused by messing with game files.
About VSync - there's always a VSync option in the game settings menu. Crytek added it in v1.1 patch. Alternatively, you can use directly the r_VSync cvar. There is also global VSync configuration inside the application that comes with drivers for your graphics card.
Lastly, if the "Internet Game" button doesn't open server list, it means that either CryMP client mod is not loaded (check if your Crysis shortcut contains the "-mod sfwcl" parameter), or your game contains some weird files (again that Warhead thing maybe?).