I'm currently the very interesting, albeit a bit dry, A House Dividing: Economic Development In Pennsylvania and Virginia Before the Civil War by John Majewski. One of the more telling aspects of Southern attempts at both building internal transportation networks and creating industry is that while investors repeatedly bought in to such schemes, unlike like in the North, they almost never turned a profit. In some instances land value along a new rail line or canal increased enough to justify the cost but only for the people immediately along the new route. But usually the lack of large cities and high population densities meant there were few markets for these improvements to service and so they, along with attempts at industrialization flounderd.
Thus, funding for improvements became very localized and just enough to increase land values for the large planters (which allowed them to get more loans to put more acreage in a cash crop and buy more slaves). In the North many locals bought shares for canal and rail companies but the real money came from bankers in Baltimore, Philadelphia, New York and Boston. In fact even the few Southern banks often were funded by Northern investors who held upward of 90% of their assets.
Another problem was that in the critical years from 1840 to 1860, 87.5% of all new immigrants arrived in and stayed in the free states. In fact the in flow of immigrants to the South was only marginally more than the rate of emigration that native Southerns had as many small farmers moved North to get better jobs. With slavery maintained there is absolutely no reason for this to change.
Also, I doubt there would be enough outside pressure to persuade the South to end slavery any time soon. It would take a major change of culture and ideology, something that didn't even occur in OTL after losing the Civil War, to make them end slavery (well they ended slavery OTL but their culture of institutionalized racism persisted for another 100 years). Besides political reality would be such that the pressure against the South would be relatively minor. Either France, to protect intrusions into Latin America, or Britain, to protect Canada, would back the CSA against the USA. In OTL the US backed some really nasty SOBs to win the Cold War, why would the politics of this reality be any different?
Benjamin