How long could slavery in the South have persisted without the war or a different outcome?

[The Mikado]

i recall listening to a podacst about the civil war saying the pop ratio between free and enslaved in the south in 1860 was like 1:6 and that was only expanding due to birth rates

...The South was not 85% slave. More like 30%, with a few states (MS, SC, LA) breaking 50% but others like Arkansas and Tennessee being pretty low.

[The Mikado]

Anyway I firmly believe that slavery wouldn't be abolished in every state within the 19th century and may have extended deep into the 20th century.

Mass agricultural slavery would definitely be phased out (economically unnecessary by the 1920s-1930s at latest due to the end of the need for that many people working in agriculture) and that that would probably lead to a mandatory deportation to Africa of a bunch of no longer relevant slaves. However, a far smaller but still real domestic slavery sector could continue basically indefinitely. The wealthy would 100% continue to hold slaves as a domestic status symbol. Living in a mansion with 25 in house slaves could easily be a major show of force and economic clout for a South Carolina aristo deep into the 20th century, as distasteful as people from other regions might regard it. Why not? No one ever gives a mechanism for how it suddenly gets abolished as an institution even with agrarian slavery's eventual decline.

Furthermore, it's worth pointing out that areas like Virginia, North Carolina, and Kentucky would have increasing call for mining in the late 19th/early 20th centuries and it's very easy to imagine slavery transitioning into coal mining.

[The Mikado]

i recall listening to a podacst about the civil war saying the pop ratio between free and enslaved in the south in 1860 was like 1:6 and that was only expanding due to birth rates

...The South was not 85% slave. More like 30%, with a few states (MS, SC, LA) breaking 50% but others like Arkansas and Tennessee being pretty low.

Say the 11 states of the Confederacy were, say, 55% slave or 60% slave in 1860, overall. How much would that have changed?

I guess it'd be easier to imagine a Reconstruction black government holding in, say, a 65-70% black South Carolina or Mississippi? The states lower on the scale would still have much the same result.