What Horace just said. Wow. And also wow.
Some lingering questions...
Regarding your question about Amy - I imagine that it is...
The things were being erased from time at every point in time. I feel they mad eit clear that this wasn't consistend or anything - something might be erased while something else might not, especially since it was happening unevenly across the universe. The Dalek invasion was erased. Probably a million events we don't care about were erased, too.
The whole "time being erased at every point in time" means there's no point in thinking about when things happened. Any event was equally likely to be erased, from a Dalek invasion to Amy's parents, to penguins (thus their disappearance from the museum).

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.