Questions about Tagalog

I've been reading bits of books on a lot of languages just out of
interest recently, and since Tagalog seems to be a bit of a favourite on
the list I was flicking through a book on it a few days ago. Just out of
interest:
1) Kumustá ("Hello", "How are you?"). Does this come from borrowing
"Comó Está?" from spanish? It seemed possible since the Spanish
controlled the Philipines for a few hundred years, and I think tagalog
only used to have three vowels, so that might explain some of the vowel
changes.
2) When two vowels are written together in tagalog, should there be a
glottal stop between them? Accents mark if a word ends in a glottal
stop, but the book I was reading doesn't make clear if for instance
Paalam "goodbye" should have a glottal stop between the a's.
3) Can anyone explain the use of a ligature in this? "para sa anak kong
si Roy" (sorry if my memory has messed it up.. I think that's right). I
believe kong is ko-ng, but I don't understand why the book I was reading
inserts a ligature here... I'm very vague on exactly when they're
required to be honest... I mean, I understand some cases, but I'm not
sure about this one.

There are a lot more questions I can think of... the language is
interesting but... well, I find the ligatures the strangest part,
because they seem to be absolutely everywhere, and looking at the
(simple) examples in this book, some of the places they appear are
places my limited understanding wouldn't expect them. A few comments on
the book I was reading too:

1) THe book tries to present ang as being equivalent in some way to the
definite article, which simply doesn't work, since each verb phrase only
has one "ang" argument, which just isn't so with "the" in english:
the man read the book
Bumabasa ng aklat ang tao (I think... again, working from my fairly
limited knowledge and memory from an hour or two of reading)
2) The book tries to present ay as being equivalent to "is" in english,
which again doesn't work:
You are beautiful
maganda ka
ikaw ay maganda
maganda ay ka * ( = incorrect)
(Hope these are right too). ay simply inverts the order of predicate and
topic...

There are lots of other things like that... the explanations I've read
of tagalog on this list, limited though they were, seem more helpful in
understanding the structure of the examples the book gives than this
book, which is weird. Anyway, I'll stop rambling on now.