Given the photos, I'd cut and scrape away all of the spray foam stuff and any raised parts of old mud/paint (like in the last pic). I wouldn't bother to pull the casing because it would probably create more problems and work. :) I might use backer rod to pack the wide gaps, then I'd fill and smooth all the large voids with mud. Situations like the last pic, I'd probably cut the raised edge of paint then fill the void with a paintable caulk.

Thanks, this is very helpful. Yeah, I don't really want to remove the casing, because in an old house things like that don't always end well.

Hi, Maybe a piece of quarter round molding that would bridge the gap and let you secure it to the casing.

Good Luck Woodbutcher

That would be a simple fix. Makes me think of the house I grew up in. Built in 1780 and it definitely settled a lot. Every time a new crack opened somewhere owners over the years would just stick a piece of trim over it. So many layers of wood in random places.