Improve my running?

First off, lifting weights isn't going to stunt your growth. The easiest way to approach this question is to tell you that if you continue to run daily, mixing up speed days with days of long runs and also a couple days rest, your body will continue to build a strong running base and you WILL become faster. It takes time and patience, it's not an overnight deal. There is no magic solution to breathing a certain way or not- as long as you're calm and relaxed while running, your body will do what it's supposed to. It's when you start focusing too much on how to breath, how to run, how much oxygen you're getting in, etc. that you have a hard time running naturally. Consider running a sort of theraputic sport where your body relaxes. You should enjoy running and the more you do, the easier it becomes to run faster and longer.