so overall it would seem that intelligence isn't a primary need for the oline, but what about the center. Should I be making sure that the center has more intelligence than the rest of the oline? I mean, do you think 10 is enough?

Personally I don't think that there are difference in the offensive linemen skill need. I base this on my experience on how the game engine seem to be built.

It would seem logic that the center should have more intelligence, like it would make sense that the tackles would have more footwork and the guards having better speed for pulling, and the list could go on and one day the game engine will probably be like this.