First it should be almost. I'm sure you know that though. If you use them, you have a complete sentence. You are saying that almost all of some individuals (previously listed) are barred from using the internet. This is less formal and is using the word as a subject. If you use whom, you have only a clause. This is more formal and it is a descriptor. You will then need a subject. For example: The kids in my class, almost all of whom are barred from using the internet, are irresponsible. It is a small distinction, but they are not quite interchangeable.

You are correct. You can use either one. "All of whom" is considered more formal. The pronoun subject is "all"; therefore, it makes no difference whether you follow it with "of them" or "of whom". In fact, you don't need to use the expression "all of", since the pronoun "all" has the same meaning. To illustrate the point: Whom are barred from using the internet. INCORRECT (Who are barred...) Them are barred from using the internet. INCORRECT (They are barred...) All are barred from using the internet. CORRECT Almost all are barred from using the internet. Correct Almost all of whom are barred from using the internet. Correct Formal Almost all of them are barred from using the internet. Correct

You would call this a text, not a script. A script is dialogue. The full sentence is, "That information will not be available to North Koreans, almost all of whom are barred from using the internet." The clause you give describes North Koreans. You can only use "them" if you make the clause a separate sentence, however this would kill the shape and flow of the sentences and make the text look a little childish. The North Koreans "are barred", so the passive construction tells me the object pronoun (whom) works best. Really, "whom" is your only option in this context.