"The reason the South wanted slavery in the territories was political. Territories become states. States send representatives to Congress. In other words- to maintain a balance in the US Congress. But if the South had gained its independence...there would be no need to maintain a balance in the US Congress. They wouldn't be there."

What U.S. territories in 1860 could support a slave economy? First of all the "South" didn't care about more slavery expansion in the territories. Only the Southern Fire-eaters pushed for this as an agenda to spark secession. They used that argument at the Nashville convention 1850 and it didn't find much favor in the South. If the territories were ripe for slavery expansion it would have already occurred by 1860-- it most certainly have occurred by 1840. The fact is the institution of slavery could not exist as an economic power in the territories west of the tree line known as the plains and desert regions. A slave owner would go broke just trying to keep his slaves alive.

This so called affront to the South that slavery expansion must not be blocked was not a popular idea with the majority of Southerners.

It was a dumb argument in 1860 and it is a dumb argument now.