The level cap started at 50 and was raised by 5 at a time through patches... they intend to eventually reach 250... though it may go beyond that as well... who knows...

Oh, and just FYI... in FFXI Dark Knights are warriors with magic ability (black magic to be exact) and higher attack, but lower defence. Yup...

Whereas Paladins are the opposite...

I heard the same thing about modifiers... but I'm not sure...

I do however think that you can use your sub job's special abilities... such as Red Mages continual magic, or a warrior's mighty strike...