Beef is a good way to get your calories up. I don't even understand someone (outside of vegetarians) not making beef a huge regular in their daily food intake when gaining. The main point I am making, is that at 15, you can get away with eating shit that most older trainers couldn't simply because of the hormones your body is releasing and the increased growth rate you are experiencing. This is not the time to try to impress anyone with how strict you can be to a "bodybuilding diet" unless that diet has the basic understanding that you need food in larger quanities, including everything from more fat, protein and carbs, to see much greater progress.
I think it is great that you have put forth the effort to learn that much about your food intake. There are people in their 60's who still don't understand what you've picked up on...but in the process of focusing so intently on the smaller details, I think you are missing the larger picture.
Your training is being switched up too much. You need to focus on forcing more food down. EAT BEEF, whole eggs, whole milk. Your basic concept isn't wrong, you just put your focus into the wrong areas for the stage of growth you are in. You are 15. There isn't a thing wrong with the occasional pizza and hamburger, especially if you are training regular.
One other thing is the comment you made about lifting fast and letting the weight down slow. This is GOOD. This concept is missed by millions (especially those taking up space doing super slow reps for no reason)...however, it makes me wonder if you are actually pushing yourself with the weight used.