My 2 cents:

1) I picked Dex on all of my human rangers. Your gonna have dex heavy weapons as your prime ones after 30 or so.
2) 23 over 20, I think that for Str, there is an advantage, but from what I understand, the real advantage for dex comes at 24... Don't have any of the edges yet.
3) still new to rangers, so I pick very bland combo's cant answer that one.
4) No clue, don't play savages, too much worry about what I can and can't wear.
5) So the big advantage that I see to Giants is this: I believe ambush takes into affect Dual wield, but I am not sure, either way, giants can wield two handed weapons(Axes and Swords) in one hand each. So you get a higher average, and with the second weapon even if you don't get the weapon hit in ambush, you will get the +Dam and +Hit. I would think that a Giant Ranger, if I were to play one, would probably not use staffs and spears much, but more mundane weapons.

I'm still working out a lot on ranger class, but thought I would put in a bit.