That may be true but the criteria aren’t clearly defined. Even in standard Get refusers, the Rama explicitly allows sanctioning the husbands kids in order to pressure him. Perhaps there’s a difference between passive abstention and proactive action, but that’s a chiddush and a fine line.
Modern justice tabooed collective punishment much more than the Torah.
I would actually disagree with this. The Rama you are citing is really an example of sanctioning him, not his children. These are things that he has to take care of, and which they are not feeling the physical effects of. He never said you cannot feed or medically treat his children. Regardless, we do know that sometimes minor children are stricken due to parental transgression, but never adult children (which is an explicit passuk), who are independent beings.
Thank you for the quotation, though. Your posts are always well reasoned, well constructed, comprehensive, and displaying formidable knowledge and understanding of the subject matters, no matter the topic.