"why is he yellow?"
This is his Shiny variant. All dragons have one, you know.
"is it OK to have this rated E and not T? i'm not sure if traces of blood count as violence"
With teeth like those, I would just as easily have assumed he bit his own tongue while trying to act scary.
"i think i should maybe leave NG because of the age limit rising and it feels wrong to use NG under the limit"
That is one way to look at it, and if you do decide to leave for a few years, that is totally understandable. Just know that you have no reason to regret it. Remember, those restrictions are not because of you or your age but because of people who never learned to "grow up" as they got older. If anything, they are the ones who should feel guilty that there are people half their age who have matured before they did. You merely came here to share your art as you continued to improve upon it. Nothing shameful about that.
"i hope i'm not being unnecessarily dramatic right now. i'm also sorry if my reason sounds stupid and/or not good enough"
You wouldn't be a teenager if you weren't "unnecessarily dramatic." That is very much a part of youth. As for not fitting in, I've been visiting this site since 2001. I continue to see posts from people in their 20s and 30s who struggle to "fit in." That's a reason why some become artists... they're socially awkward. Art helps them to express themselves when they have trouble doing so directly.
TL;DR version - Toggle thought he could get away with only flossing right before his dental appointment and now the pain in his mouth is making him cranky.