how to get to FuYong ferry terminal from Shenzhen North railway station? the schedule and the cost?

You can take direct bus no.330C at the North Railway Station. The ticket fare is CNY 24 per person. The operating hours are from 5：00 to 20:00 with the duration of 45 mins.
After that, you can find many free shuttle buses that can take you to the ferry terminal directly.

And yes, North Railway Station and the airport open 24 hours. But it doesn't mean that the stores and restaurants inside these two place still open at the time. You can stay at the public area. :-)