OK, let's see if I got the rules right... All your abilities start at 8. You don't get extra points by lowering the scores further.
You get 28 points. All racial bonuses are applied afterwards.

So, is my dwarven ranger a valid ALFA character?
His scores: 14 str
10 dex
18 con (including racial bonus)
12 int
14 wis
6 cha (racial penalty included)

I used the Character Generator Demo but it uses the roll system, so I'm not sure. Also, I've read somewhere that you'll be able to reroll as many times as you want in NWN. Is this correct?

Any help is welcome!

Last I heard they are using 25pts in the NWN game as it ships and ALFA are using 28pts.
If you click on the roll screen on the generator demo you get a dropdown menu that gives you the pointbuy option. The default value is 25 but you can change it.

Thanks a lot!