looks a lot better. i don’t think you need to worry about his feet moving. lots of sprites do the same thing and it looks convincing enough.
You made some really great changes. I think the best change was off-setting the timing on the bob of his body and the bob of his gun. That made it look way more natural.
My main critique between the two images is that you distorted the butt of the gun a bit. Instead of more or less going straight behind the barrel, it looks like it is bent downwards and maybe even a little ways away from the viewer in the z-axis. I might also try a very dark grey in lieu of pure black for the barrel of the gun, as it makes it look awkwardly pixelated compared to the rest of the image, because it looks like an outline for the body of the gun instead of the barrel at first glance.
I don’t know what background you have in animation, so I’m just going to throw out a reference that I think is invaluable to anyone serious about animating in any capacity.
Amazon.com: The Animator’s Survival Kit (9780571202287): Richard Williams: Books
This book basically covers all the fundamental knowledge needed to make convincing animation scenes and sequences. Everything from timing and spacing to walks, accents, and dialogue are covered. No animator should be without this book to use at the very least as a reference.
From the looks of it you have a solid drawing background so you’ll have a better time focusing on the concepts that are introduced in the text. But understand that animation is a discipline unto itself and there are certain rules you have to internalize before tackling major projects like the one you are proposing.