Just redraw him in two distinct STEPS, and I seriously mean REDRAW as in you mark out his most important proportions and then draw him all over in stick figure fashion, then make transition frames until you have a walk.
Your workflow seems sorta sucky, animating legs below a static torso is just making stuff hard for you. Redraw redraw redraw. After that you can copypaste parts that don't move or change a lot, like, well, the head.