correct me if I'm wrong, but if your off-hand is not benefiting from an expertise racial I believe its perfectly viable to go 7.5%/6.5%. Not sure exactly what you mean with the last question, but Orc is the best option on horde side and Worgen the best on Alliance side, regardless of weapon setup and expertise bonuses
1.) No. Offhand expertise does not need to be capped, and capping it will result in a loss of stats that are more valuable reforged otherwise. So 7.5%/6.5% is fine.
2.) You want the MH to be expertise capped.
3.) Orc or Worgen. I'm not sure if the AP on use of orcs is better than the 1% crit of worgen. That being said, there are several axes this tier (for orc expertise racial), although none are BiS unless you're arms/TG Fury.
Another chime in for 7.5/6.5. I ran a bunch of sims after going Orc recently, and I'm using axe/sword combo reforged to 7.5/6.5 expertise after running SimC to find the optimal weapon (I have another elegion around) and reforge combo. Of course, it's always best to sim yourself to make sure.