You shouldn't be asking their spouse how their marriage is going. If you don't like someone, what do you care how their marriage is going?

You shouldn't be actively celebrating their misfortunes. If you do not like them they are not worth expending any time or energy on. Even if it is to celebrate their misfortunes.

You live your life and they live theirs. If you happen to be related to them by marriage, simply treat them with respect when you see them and don't shred them to anyone who may repeat your words to them. Don't actively exclude them. Most of us know nobody wants a stepparent, know you're not our fans, and want our husbands to have good relationships with their kids. Therefore, we do not need you telling us not to come. We already decided not to. You don't have to love or like these people. But if you dislike them, don't take any action relating to them at all. Let them figure out what they want to do and you do the same for you. *

*However, if the SP does decide to come, do treat them with respect and make sure they are treated with the same inclusion you'd want shown to your SO. Try it. You will become (and feel like) a better person. It's not like you have to see your SP a lot.