Thanks Decroded for your advice on the hand and belt area. It still needs a lot of work and I think I'm willing to perfect this sprite with the help of this forum, considering I am no expert at all. I had also tried to animate the feet in a subtle way as u suggested, but didnt have much luck :\ maybe someone could help me in that area?
As for the anatomy, I had considered shrinking the head's height a bit overall but I don't want to rip off Paul Robertson's style too much. I feel like I'm already ripping off his body style, and I do want the game's art too look somewhat unique. Also, about the crouching to dodge an enemy punch, I could probably have the character block instead and have an almost equivalent result to avoiding damage and/or hits.
And the problem with the hip, I agree, does make the piece look quite stiff. The legs and lower region need some serious improvement I would say, which is why I came here. I haven't been able to really fix some of these errors yet, but am looking forward to more advice the more I update.
Thanks again, all of you, for your comments. Please continue to share wisdom and advice with me for this piece. I'll update it as soon as I feel like I've made some improvements to the animation
EDIT:
Oh, and I forgot to mention, any tips on how to minimize limitation on gameplay due to the character's head size nature would also be much appreciated! For example, shrinking the head size a little, or another method? I want the game to still have the feel of a classic beat em' up game and hope to not be limited to vertical stiffness as yrizoud said.