1. Used to be a favourite on ADC oral boards - What do you do? A. Ask lander where he'd like to divert to... Q. But he declares a fuel emergency, etc, etc.. Obviously not much can happen until a) you have another runway or b) the u/s a/c has been cleared - and that should only take a short while.. If it's a long runway maybe the landing distance could be revised and some a/c might be able to land - check with airport authority... For other landers think about other nearby airfields... There is no real answer... they'll just be seeing how your thought processes work.
2. Dunno anything about Atlantic tracks but seems a bit complex for you to be expected to know about. Having said that, in my very first ATC interview I was asked what sort of separation standards are applied over the ocean!
3. What do you want to know about approach sequencing? It's basically a system using radar applied at busy airfields to achieve the best landing rate.