I think the head rotation looks quite fine, and feeds a zany cartoon characteristic, and 1 major problem which is making it hard to judge the animation at the same time, is one one frame you have the red and blue limbs flip, so essentially for one frame he spazzes out and swaps his foreground limps with his background limbs, but yeah I think the attention needs to be paid to the legs, legs don't generally bend up, so in one of your frames you need to raise the knee, or drag below the knee back toward him, which will help with the leg length issue Alex raised