Books on the Usage of the Modal Verbs

What books would you recommend to learn more about the modal verbs? I've written here, on alt.english.usage and on uk.culture.language.english; I've read tons of messages in the archive of this newsgroup (particularly a thread of 137 messages, http://snipurl.com/3kvp, recommended by Mike Elwood), but I realize even you anglophones don't know your mind that much or you don't agree with each other, at least.
Everybody says something different:
1) Somebody says there is no difference between "shall" and "will": whatdoes that mean? May I use either "shall" or "will" for all persons? I really don't think so.
2) Somebody says the traditional grammar books are right ("Ishall/you-he-they will" for plain futurity and "I will/you-he-they shall" for intention, promise, duty etc.). If so, the rule doesn't seem to apply to questions, where "Shall I?" expresses an offer or an inevitable future and "Will I?" expresses a plain future (I guarantee I read it in the afore-mentioned thread, "Shall and Will in Other Languages"), only "will" being used for second and third persons.
3) Somebody asserts that to forget "shall" would be the best thing to do, orto use it only in offers.
Well, I'm actually looking for a book dealing with the modal verbs (particularly shall/will vs. should/would; but I think I should know more about "may" and "might", also), a book which should tell me:
1) if the usage of "shall" vs. "will" must be consistent with the usage of"should" vs. "would". In other words, if I ought to use "should" where I would use "shall" at the present tense and if I ought to use "would", where I would use "will" at the present tense.
2) the evolution in the usage of the modals: the situation before the 18thcentury (in outline: "shall" for all persons to espress an inevitable future or a plain future and "will" for all persons to express intention, I suppose); the traditional rules (please, don't recommend to read that page from "The King's English", since it was my ruination; the current situation, that is to say, colloquial usage, correct usage based on practice etc.
3) the main differences between the usage of modals in England, Scotland andIreland (I just know they have always ignored the difference between "shall" and "will", but what does that mean?) and the Usa (I think Americans tend to quite ignore "shall", but that's it). Just to get an idea of that, not a historical treaty on the modals, God forbid!
and should warn me against the legends handed down by grammar books.

I'm not looking for a book that should me about the usage only: I would like to understand, to be aware of why I use "will" and not "shall" (the same for "would" and "should") and vice-versa.
Is there such a book? I was recommended some books but they're old or superficial, then I'm sure I couldn't find useful information on them.

At school I was taught to always use "will" ("shall" only for polite requests and offers with "I" and "we") and "would" ("should" only for conditional duty), but I can't deny I often find "shall" in British English, as well as "should" to form the conditional.
I've read the parts of "A Practical English Grammar" about that, but it just says to use "I/we shall, you/he/they will" to express plain futurity and "I/we will, you/he/they shall" to express an intention, a promise and so on (it specifies that "shall" for 2nd and 3rd persons is quite odd, if not in contracts and similar documents, and that "will" may well carry a plain future meaning). It doesn't mention, for instance, the proper usage of "shall" and "will" in questions which seems to me inconsistent from their usage in affirmative sentences (I don't think "Will I?" expresses willingness, as much as I think "Shall I?" is only used in offers and not for plain futurity).
I've learnt to distrust most grammar books and, above all, what I learnt at school. Still, I feel that bare practice is not the way, then I think I would need some reliable reference based on grammar (correct usage), and actual current usage (especially in correct British English).
Bye-bye, FB