You're not going to be gaming at 1080p. Not with a good framerate, at least. Definitely lower the resolution, 1280x720 at the most. Settings as well, I'd use low or medium presets.
You should consider adding a graphics card if you can afford it. A non-Ti GTX 750 would be a good fit. There are models of that card that don't need external power and they will run on relatively low amounts of wattage/amperage.