1. Yes, unfortunately, it does.
2. Sure.
3. Quirky, classic, uncommon.
4. I suppose, however, that sort of thing doesn't matter to me.
5. Honestly, I don't care for
Posy. It seems a little lightweight to me and probably isn't ideal with the surname. Yes, I think the nick should sound nice paired with the surname. After all, she'd go by her nn more often.
My fave nn for
Rosemary is
Romy. I adore that but I'm not sure it would be any nicer with your surname.