>>92
You can't say ないなさい, it doesn't work that way. If you really wanted to use なさい you'd have to go with 怒鳴るの（を）やめなさい. Also it's not polite - though I'm not sure giving someone a command is ever exactly polite in any language, really - it's just more polite than some alternatives. The most (stereo?)typical situation to hear it used would be a mother scolding her child, and it quite often carries something of that tone of admonishment.

That and ください is a command - in it's in the imperative form! If you hear it used in the right situation it can really drive home this fact, and it can also sound very cold if you're not careful about how and to whom you say it. If you really want to be asking rather than telling you need to go with くれませんか and so forth.

I think a textbook sentence for this would be as >>90 said, although I think 叫ぶ would be better than 怒鳴る. I'm not sure what you mean about なら sounding like "since", but to me it feels way more natural than ば in this sentence.

My sentence would be like 英語を勉強してねぇなら英語で叫ぶんじゃねぇぞこのボケが！ I think it has more... character.

>>96
I don't really want to explain conditionals because it's a pain in the ass and I think in some ways explanations and rules aren't going to be much help, you just need to get a feel for how people use them. Especially since they will break the rules and use them in ways you might not expect; for example, people use と a lot more than a description of its uses might lead you to think. I will, however, give it a shot if there's any specific aspect/usage you want explained.