The 2/3 only applied to slaves, not to "non-whites" in general. "Mexicans" and (actually Tejanoes) and free blacks, were fully counted. Actually it would have been better if slaves weren't counted at all, since counting them resulted in over representation of the slave states in the US House.
It didn't have to take a war to change that situation. A consitutional amendment would have served as well, and been a whole lot cheaper too. Now, the southern states *might* have seceded if such an amendment were passed, but that would have meant that slavery remained legal in the Confederacy but not the Union, but would not have changed the economics of it. It would likely have died of it's own weight by the 1890s or so, if not sooner. Slaves were expensive, $1000+ in "then year" dollars was not unheard of, and expensive to maintain. Irishmen were much cheaper for most any job. Chinese were slightly cheaper still, and it one died on you, there was another stepping off the boat to take his place.
Trully amazing! With one exception, you did not have to buy EVERY slave. If you had a male slave and a female slave, you could let them mate and then have their little slave for FREE. You need to listen to Jimmy the Greek tapes. On the other hand EVERY Irishman and Chinese worker had to be paid. You are absolutely nuts if you think OWNING a slave was more expensive then highering workers.+