What kinds of problems would ending slavery have caused the nation before the beginning of the civil war?
I think that the problems would have been much the same as they were when the country ended slavery after the Civil War. The country would have had to deal with the issue of what to do with all those freed slaves. The one additional issue would have been the issue of paying for the freed slaves. The country would have had to work out whether it would pay the slaves' owners. If it did, it would have had to come up with the money to pay for that.
Outside of this, though, the main problems would have been the same. The slaves were a group of largely uneducated people with few skills. Once freed, they had to be given a place in the economy -- one that they could do but which would not just amount to a return to slavery.