Is there a way to get hair past it's terminal length?

there is no such thing as a terminal length, especially at you age. just take care if it. a way to get it to grow would be to never heat style it for a long time, like over summer. just put it in braids, or scrunch it. it will grow a lot. you need to start trimming, it. that split ender thing isn't gonna do squat. just condition, get regular trims, and lay off the straightening. good luck.