Is it possible for custom characters to use force lightning? I read online that you have to buy/unlock Dooku and use his lightsaber for your custom character.

I have already unlocked Dooku but his lightsaber is not at the custom character screen. Is there something else I need to do?

Also is Darth Maul's lightsaber available for custom characters as well, if so how?

Where the hell did you hear this? No, you can't get a custom character with Force Lightning. It's only for regular characters (Count Dooku, The Emperor etc.) and the red lightsaber can be used. Look closely next time...