Grammar Schmammar

Recently I have been posed quite a few English grammar questions that I was more-or-less able to answer, but had no idea how to explain. I vaguely remember studying the rules and explanations in school, but have long since forgotten most of them. It seems almost daily my co-teachers (JTEs) approach me with a question from a student. I am fairly certain the JTEs know the answer (their grammar knowledge is far better than mine own), but ask for clarification, or maybe just to test me.

Example: Consider the case of "any" and "some".

I have some apples.

I dont have any apples.

Can you buy any / some apples?

Are there any / some apples?

I cant begin to explain this in English, much less attempt in Japanese.

Or how about this?

I have a headache.

I have cancer.

When to use "a" and when not to use? I know, but cant explain why.

Also, there is great confusion as to when to use "a" and when to use "the" before nouns.

This next one too, had me baffled on how to explain:

Who is the teacher? Ms. Sato is. (this part very clear)
Who is Ms. Sato? The teacher is. (??? why cant we say this???)

Japanese is not a subject-verb prominent language, rather it is a topic-comment prominent language. What does this mean you ask? I am quite uncertain, but it makes for difficult translation. Actually, I do have a foggy idea of what it means, perhaps I can expalin. Sentences focus on the most important element of the intended communication and how the other elements relate to it, rather than always the subject and verb. Often in Japanese, the subject can be understood from the context, and is omitted completely. Verbs always come at the end of the sentence. Recently I have been tried several times an activity in which students choose a new word they dont know from their dictionaries, partner with someone, and then must write sentences with the two new words. It works quite well, but naturally, students craft the sentences in their heads in Japanese, and then try to translate them directly. We end up with sentences like these (in parentheses, the intended meaning in Japanese sentence structure format)

"The puzzle can use all generations". (As for this puzzle, it can be used by all generations).
Obviously, a better English sentence is "All generations can use this puzzle".

"This theater can take a meal." (As for this theater, one can take (have) a meal (there))
or "One can take/have a meal at this theater."

"I surprise this puzzle." (As for me, this puzzle is surprising)
or "This puzzle surprises me."

As you can see the manner of thinking when constructing a sentence in Japanese and English is quite different. Add the many rules and exceptions to rules of English and you begin to understand what a frustrating language it is to learn (and why Japanese is so difficult for English speakers).

It is probably quite clear to you now that I have become a grammar geek. Its quite true, but writing this has made me tired. Just to irk my mother (my long-standing grammar correcter), I am to going to lay down for awhile. I just dont know where at.