They didn’t force already existing marriages to be dissolved, but didn’t perform new ones, as far as I know.
Secondly, when someone does enter polygamy, unless there are attempts you can catch at multiple concurrent marriage licenses, there’s not much you can do. Plenty of people cohabitate plurally without marriage licenses nowadays, and that’s the real problem in Utah, a “polygamist” is not legally married and therefore can be in the closet about their “polygamy” for some time. They can infiltrate, appearing and coming out at a convenient time. I would argue that people shouldn’t be living apart from the rest of society in compounds, but in communities with the rest of us, that makes them a whole lot easier to catch or not condone. I think it’s something our pastors could address as unneccessary and to some extent, something that has caused trouble for us on the welfare bills we pay to support these cults.
Yes they did. B. Carmon Hardy even lists them by name in his appendix of his book Solemn Covenant: The Mormon Polygamous Passage. About 250 he was able to document (& who knows how many undocumented) -- between 1890-1910.
That's actually why the Lds "prophet" had to issue yet another "proclamation" on the matter in 1903...because Lds authorities under him were ignoring the 1890 proclamation.