Get Radeon pro, create a new profile. Select the Crysis 3 .exe file (Don't have crysis 3, so don't know what it's called). Turn AF, AA to off, make sure VSync is disabled. Change the mip-map settings to "High performance", tick the "Disable Aero" box, limit the framerate to 30fps.
Then, OC your card.
After that, turn down the resolution to 640x480. You might get lucky and pull of 30fps.
5450 is the worst card you can get for gaming. It's more like a cheap card that makes you able to watch HD on your computer. I had 5450 HD card and coudn't play anything while my old 8800 GT was kicking it's ass. I could play Batman Arkham City with my 8800 GT while the 5450 was giving 5 fps max!.
Don't even try to play modern games with that card. It simply won't work.