The cylinder moving back while open is a function of the small raised lug on the frame that holds the cylinder from moving back when open. Some movement here is normal
Does the yoke itself move forward in the frame and get a small gap between its surface and the frames? If so the yoke screw may need replaced or the "button" on tip of yoke pivot adjusted a bit.
The .003 difference from pressed back to pressed forward between the barrel cylinder gap is called your endshake. While .003isn't horrible a simple .002 endshake shim would tighten it up.
But, really a small amount of movement is normal when cylinder is open. As long as it locks up well when closed, its in time and the endshake isn't much more than it already its probably just fine for shooting.