You have asked a bunch of good questions. I will give my best answers to a few of them.
Regarding whether to shim the hammer for side play, I personally stop working when my actual problems are fixed. You had a problem with the hammer rubbing in a way that noticeably affected the action. That problem is fixed, and you have not made any non-reversable changes. So this is a good time to stop.
Some people continually chase perfect specs, but that is not always a good thing. A pistol which performs very well, but has a little play in the right places, may be less affected by dirt, and therefore more reliable in the long term. I do not try to tighten revolvers if they are within proper specs and working well.
An alternative view is that testing with shims is non-destructive, so it is fine to add another shim and see if you notice an improvement. In the worst case, you just remove the shim and there is no harm done. If you are enjoying working on the gun, there is nothing wrong with this course. I will mention again though, that tighter is by not always better. And the feel can be deceptive if the gun is impeccably clean in the workshop.
Regarding the double action sear, try using a sharpie marker to examine the wear pattern and see if it is square. Mark the sear and the trigger with a sharpie marker. Then assemble the revolver and work the action. Then take it apart and see where the parts touch. Be aware that when you begin examining parts this way, hardly anything is ever really square. So an uneven pattern does not mean you need to "fix" things with a stone. But if you do want to adjust something, the wear patterns tell you exactly where to do it.
If you want to remove the sharpie marker, it will clean off metal with rubbing alcohol. Or if it is out of sight, you can just ignore it.
As an example about parts fitting, on one of my revolvers, the double action sear was only making a thin line of contact on one edge, and the hammer was rubbing on one side. I stoned just enough to get a bit more than a millimeter of smooth contact on one side of the sear and trigger, and that was enough to resolve the issue, so I stopped. I did not try to stone it until the wear pattern looked "good." The pattern still looked pretty poor when I stopped, but it was much better than it had been, and the problem was resolved, so to me that was enough.
