Abilities and skills aren't halved for the sub class. A 10th level fighter / 5th level white mage has all the same abilities and theoretical skill cap as any 5th level white mage, primary or sub.

Also, there no extra skill points to assign during character creation. All race/class combinations will be idential stat wise when compared to same race/class at any level (equipment not withstanding).

And ShadowDragons.com has a lot of useful information, but don't expect a site that has everything, I've looked, it's not out there. Just get on google and type in Final Fantasy XI and start looking around, there's a lot out there, you just have to do some of the digging yourself.

Leighton