The 0.8g/lb of protein number is the amount of protein a sedentary individual needs to consume to maintain their muscle mass. Most studies conducted by the FDA are not conducted on, nor geared towards, athletes. With the amount of activity that you are doing, you definetely need to increase your protein intake, regardless of whether you are trying to gain mass.
Also, at your age your metabolism is in overdrive, and judging by your build (based simply by your physical stats), you have a naturally fast metabolism to begin with. This means that you must consume substantially more calories than 2500. In fact, 2500 calories probably doesn't even cover the amount of calories your body needs to function adequately. Remember, at your age your body is going through one of the most substantial growth periods in human development. This means that it requires a lot more calories than would a fully grown adult.
I would suggest that you consume at the very least 3000 calories per day. And to be honest, you should probably consume more than that.
Up your protein and your calories, then wait 6 month and see if your gains don't substantially improve.
One more thing I wanted to mention, an Endomorph does not need to eat a lot to gain muscle. Endomorphs are generally large, husky individuals who put on weight (muscle and fat) extremely easily. Ectomorphs on the other hand do need to consume lots of food to gain weight. My guess is that you are an Ectomorph. Just wanted to clear that up.