"It is currently closed."
Translation:Il est actuellement fermé.
Maybe this will help you: http://www.frenchtoday.com/blog/cest-versus-il-elle-est
Yes, that's fine. Long adverbs can go at the beginning or end of the sentence (unless they directly modify the verb).
Well, it's not as random as that makes it sound. «Fermé» is the past participle of «fermer» (to close), and it's just used as an adjective in this case.