Your problem is that your character isn't "falling forwards"
You see. When we walk, we fall a bit forward and then fix our stance by moving our feet forward. The same thing is for running but we fall much more and move our feet faster.
Cartoon 3d models look like that sometimes, it is pretty good. Remember to push the inside of the nose and mouth far into the head if you have not done that already. You did a very good job at the hair and eyes, the render doesn't look that bad either