I belive even manga style follows tradicional anatomy, only represented with slight changes in style and simplicity.
I think that for a 14 year old something like "anotomy? i happen to think my anotomy is pretty good" is a pretty bad line. at your age, you should focus on learning, not beliving you know everything. even if people's sugestions apear wrong to you, there is allways a reason why they gave them in the first place.
as for you piece I think you should really let go of the thick black outlines. pixelart isn't doing anything for pieces this big. you should think if you want to be a pixel artist or a digital painter.
the nose is badly represented. no matter how much you think it looks like yours, no nose would look like that in thoes lighting conditions. the way the position of the light is sugested ( above, slightly to the front and to the right) the nose should never have that black line, or the nostril blend like that with the cheeck.
look at your self in the mirror and see if you are getting it right.
a personal tip: if you are 14, don't just jump into Manga so soon. you'll become to much tied to that style. belive me I know. I've seen great manga artists that can't do anything else. you are in a good age to learn, don't force your style.