Question: Have you read Life as We Knew It by Susan Pfeffer? And also, do you think an event like this is likely (an asteroid hitting the moon, making it come closer and making bigger tides, volcanoes erupt, etc?)

Wow, sounds like a great novel!
I haven’t read that one 🙂
To answer your question, you’d probably need to ask an astronomer or physicist, who are interested in space science and gravity. But from the little that I know about this, I think it could be possible that the way the moon orbits around the Earth could be changed, by something like an asteroid, and this would probably have effects on tides-don’t know about volcanoes though!
The orbit of the moon actually changes anyway, this is called pertubation.