The brown sugar gives the cake a really dark color and a nice flavor. You can use normal sugar in its place.
You can skip the coffee but coffee ups the flavor of the chocolate cake, so it is highly recommended.
Instead of boiling water, you can use warm water as well. However, I preferred the texture of the cake with boiling water than warm - it was much softer.
You can bake in a normal round pan or even a loaf pan. Bake for around 40 to 45 minutes till done.