Another thing that worries me is that I don't see detailed characters in games, especially mobile, everything is small or pixel art, so maybe someone can explain that to me too.
Well, with 2D games in general, large characters aren't used often I think because the player generally wants to be have a decent view of the stage and the action. If your characters are large and everything else is proportional, then your player isn't going to be able to see that much (and might not feel very in control). I guess this'll vary from genre to genre, but.
It's especially something to keep an eye out for on mobile, because those screens are generally so small you don't really have that much room in the first place. Chunky, stubby pixel characters both "read" easily and don't take up too much valuable screen real estate.
(Also this might just be me, but I always associated 2D platformers and stuff with huge character sprites with bad movie licensed games.)
I'm actually not that bothered by the anatomy, since it seems like you're going for more of a cartoonish style. If you do decide to keep the outlines, I'd suggest playing with the thickness of some of your lines for more variation.
I don't know if this 'cartoon style' is really up to the quality level where line weight variation would help much, honestly. Heck, it kinda makes me think of highschool notebook drawings in ballpoint pen. You could even embrace that and make the lines messier/scribbly to complete the vibe.