Thanks! I actually solved this late last night, mostly using method #2 (resizing the max width allowed for the various elements in CSS). Many of the individual elements already had the img width line you included, but they were set at 100% with the !important designation on some (and changing them to 99% didn’t work), so I changed them individually to pixel widths. (It was a little different in each area, so I just experimented til I found a setting for each that didn’t cut off the border.)
Again, if this helps anyone in the future: I worked around the border cut-off issue by changing the CSS max width setting (inside a child theme) for each area where the image border was getting cut off. I’ve also started making new images, including “featured”, not quite as wide as they were.
Thanks, again.