По первому пункту:
Может, Вас такое устроит?
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К каждому переносу строки \\ я добавил \\[6pt]
-- 01 дек 2010, 11:19 --По второму:
Like LATEX’s \pagebreak, \displaybreak takes
an optional argument between 0 and 4 denoting the desirability of the pagebreak.
\displaybreak[0] means “it is permissible to break here” without
encouraging a break; \displaybreak with no optional argument is the same as
\displaybreak[4] and forces a break.
If you prefer a strategy of letting page breaks fall where they may, even in the
middle of a multi-line equation, then you might put \allowdisplaybreaks[1]
in the preamble of your document. An optional argument 1–4 can be used for
finer control: [1] means allow page breaks, but avoid them as much as possible;
values of 2,3,4 mean increasing permissiveness. When display breaks are
enabled with \allowdisplaybreaks, the \\* command can be used to prohibit
a pagebreak after a given line, as usual.
(displaybreak означает разрыв выделенной многострочной формулы)