It does seem a lot. Have you been napping a lot today? I find I need less food when I sleep a lot, but I'm not sure if that stuffs up the metabolism or not.
I'm not too sure about this issue. My guess would be that as long as it's not a daily occurrence it's not too bad to be well under your calorie count for one day. If you're worried about it being too much of a deficit then you can always have a handful of nuts. They're packed with calories, but also contain a lot of protein so they're a nutrient rich way to make up the shortfall.
Sorry I couldn't be more help!