If you get the error "FPS_Limiter.exe: Could not create game process", go to FPS_limiter.exe properties and at compatibility click at Execute as administrator and it will work.
You can test in a CMD window at fps_limiter folder with the command:
FPS_limiter.exe "PATH to FSX.exe\fsx.exe"
All the other switches you want are default.
If it works just write in a batch file the following command, in my case:
start D:\"FSX\fps\"FPS_Limiter.exe /r:D3D9 /f:30 /x:OFF /l:OFF "D:\FSX\fsx.exe