The right leg when it's forward in the walking animation with arms looks like he misplaced his hip. =/

Here's a good hint, try and find a camera you have, any kind, and then take a photograph on yourself while holding the camera above your head's height.
That'll give you a better idea then what any words ever can say.

Sometimes it's good to have reference after all.

Firstly, everything in your sprite is more or less 1:1 proportion on the angle, he looks like he's just in our straight eyeview. You need to make him look down firstly, and then reapply that setting to the rest of his body. The Red line shows you why it looks like he is walking to us, as that's the angle you see. If you move your camera more upwards into the sky instead, most of his proportion should shrink on main body, as seen in my doodle. Also tilting all the details as well.

Let's begin there, shall we?

Oh thought the clothes looked rather modern on your 2 main spritesheets.

If you want him to look young, make a portrait of him to make it more obvious.

And somehow he looks more of a death skull spartan, which isn't that bad. He looks solid enough. Maybe make his legs longer though to keep the proportions better.

Try and round the hair that works as well.

And somehow that face reminded me of a game, but couldn't pick which, Guess it might be from there.

Let me guess, Tōshirō Hitsugaya from Bleach DS game?