For your second question, I can confirm that you both need to be there and in a party to schedule a ceremony -- even when it's a rescheduling. It's best to be there when they open up the week you want to schedule during (to prevent "your" slot from being snapped up by someone else), but if one of you can't be present at that time (due to work or sleep, for example), there's a somewhat sneaky workaround to that, since the only requirement is that both your characters be present and in a 2-person party. One of you being afk works.