Intensity on 14, fan on 65%, temps at 77C. Don't I want to stay below the 85C range?
Also, I can get exactly 300 if I put intensity to 18 and fan to 100%, but that's going to kill my card. I don't overclock, either. I'm using this computer as my only computer as well.
Try to play around with some of the settings listed in this hardware comparison:
https://litecoin.info/Mining_hardware_comparison
Intensity should definitely be higher than 14 if you want higher hashrates, but check your thread concurrency as well until you find the optimal number. Lastly do not forget to adjust your clock speeds for optimal performance since that will likely have the biggest impact. Some cards get higher hashrates when overclocked while others get the best results when they are underclocked.