Nice update arq, let's see now.
ok, the animation looks a bit slow in comparison to the game.
Every key frame lasts for 6 tics, so Key frame, 2,3,4,5,6,Key frame,2,3,4,5,6, key frame....
The Key frames are where you actually make the pose to begin with, blocking it out. Maybe you don't need every single key pose, depends on the animation.
I try to get as far as I can with that first, not adding extra frames in the tweening gaps unless it's unavoidable. The less frames you have the easier it is to work with, less confusing
I work with max set to 60 fps on the timeline and render the animation at 30 fps by limiting the render option to every other frame.
Right now, from what I see in your animation, I'd fix the timing first.
Next focus your attention to different parts of the original sprite animation vs yours, tunnel vision.
If I focus on the hips, I notice that he should be moving forward and back more.
His body is sort of arching like a C, you have it too straight.
When he moves his Left arm back, he arches his spine side ways a little.
His Left foot may need a key frame removed to fix that wiggle, or you need to straighten out the motion curve.
The Right arm looks like it should twist in and out a little, look at his hand. Same with his Left arm, his hand rotates.
Keep looking at different areas, the hands, the head, etc. Imagine a rubber tube, whip or a bouncing ball to get an idea of how to get rid of the stiffness in the arms and head.
You can act the movement and feel the difference also.
Make sure to use the motion curves to fix your in and out timing, and control the trajectory.
The Left foot for example, It may be an extra key frame or it could be that the motion curve is too loose / arching too much.
The shoulders are blending too much with the traps, you may need to edit the mesh a little.