Dear Lance,
1. Diet is a question of protein sufficiency, then calorie adequacy, depending on your goals. To gain weight, you meet your protein requirements and have an excess of calories from carbohydrates and usually, fat. To lose weight, you meet your protein requirements, and might take a little more whilst you cut overall calories by restricting carbohydrates and fat. In both instances, the componenet of weight loss is two-fold - muscle and fat. Individual biochemistry and all such normal variance will determine how much muscle and fat is gained/loss per pound of weight gained/lost. On the HST FAQ, there is a section actually discussing ratios, with protein being around 15% total calories. To be honest, my opinion of this is that it provides a theoretical framework on the biochemical effects of food. But have a read of it and see
2. At your age, your hormones are or should be raging. Furthermore, your gains could be beginner's gains - you will not be gaining so much so soon for all the years to come. Bearing this in mind, I hope you do not despair when the gains begin to slow down.
3. I am assuming you have an idea as to calorie intake and all such nitty gritty. Since your abs are visible, you can begin some serious bulking. All else being equal, more calories = more growth, and the combination of ample calories, a sound training program (ala HST) and sufficient rest can work wonders.
4. If I might be so bold, I beseech you, have a read of the HST principles, verify the references on PubMed. Give them some thought, a lot of thought, and compare HST with other training programs. How many out there are grounded on science as opposed to the hocus-pocus "it's seen to work in the gym, it's about the intensity" pseudo-science nonsense?
5. To answer your question - if you stick to the way you've been eating, you will eventually cease to make progress. This is because, as your body grows, you'd need more food. Don't just stick to the same diet and amount - increase calories as you go along. And if you wish, there is no need to take tons of protein. 2gm protein per pound of bodyweight already is overdoing it, and if you are in caloric excess from ample carbs and whatnot, even 1.5gm protein per pound of bodyweight is plenty. Individuals on a protein sparing modified fast take 1.5gm protein per kilo of bodyweight and this actually prevents muscle loss. Whack in a good dose of carbs (e.g. several pounds of potatoes, rice, pasta etc) into the equation and I dare say that 1.5gm protein per kg of bodyweight would suffice for growth.
Congratulations on your progress, and a very warm welcome to the realm of HST
