To me, that is exactly what the latter sentence means. If Alice and Bob have two different sets of kids, I’d use the first construction. If they are the parents of the same kids, I’d use the latter. Neither sound awkward to me.
Which is kind of funky since I would still pronounce it “Anguses” if I were speaking it. If I were to read it, I think that in my head, I’d just hear “Angus”.
Depends on the style guide. It’s “apostrophe s” for Chicago Manual of Style and Strunk & White, and bare apostrophe for AP style and MLA. Now that I no longer work in journalism, I default to Chicago Manual of Style.
And there are styles (like New York Times) where it’s “apostrophe s” if the “s” is not pronounced at the end of the word being made possessive (“Arkansas’s”) but bare apostrophe if it is (“Kansas’”).
I prefer apostrophe-s in all cases.
ETA: And then if it’s a common noun, there’s another set of rules depending on the style guide.
Same here. I get it when I read it, but it doesn’t parse as ‘Anguses’. Doesn’t seem to be necessary to have this exceptional case, “Angus’s” works just fine.
ETA2: Meant to append this to the above ETA: AP has the most convoluted one with apostrophe-s at the end of a common noun to indicate possession, unless the following word starts with an “s.” So, “waitress’s uniform” but “waitress’ shoes.”
Interpretation is dependant on context. In some contexts it would mean one, in some contexts it would mean the other, and usually it would be obvious which one is meant.
Without any context, most people would assume the first meaning