Great questions! I hope I can jump in without being too short.
I wonder if something like debatemap.app or kialo-edu.com would offer a better UX (“user experience”) than Lemmy. I’ve also heard that substack.com has done a good job of attracting high-quality discussion (but I worry, what’s stopping them from traveling down the enshittification path like all the rest?)
OTOH, I think online discussion itself has some weaknesses that can’t be easily overcome–perhaps in-person, local discussion is (usually/almost always?) better. For example, one study indicates that engaging in political discourse with people online leads to an “uncivil comment rate” of 10%, while a “mixed political / non-political” discourse has a lower uncivil comment rate [1].
Personally, I find it to be generally true that I need to trust someone in one or more non-controversial areas of life before I take their controversial (to me) opinions seriously. Simple time and familiarity also helps.
[1] https://www.frontiersin.org/journals/political-science/articles/10.3389/fpos.2021.741605/full
I’m sorry for your suffering and heartache. I wish you the best.