Immersive Shane apparently does a big improvement on him, but I haven't tried it or married him. Sebastian has a 7-event post-marriage arc which involves his family and his relationship with the farmer both. It's a bit talky but cute.
I know Abigail doesn't really have any post marriage mods (or even really any exclusive dialogue mods). Leah has a post marriage dialogue mod but none pre marriage and I don't think any new events. Elliott has at least one plus an extra event adder.