Kevin S. answered 12/01/19
Bachelor's Degree in History from Slippery Rock University
The simple answer to the question is yes, it was inevitable assuming of course the ending of the institution of slavery was ultimately inevitable. By the election of 1860, slavery was so vital to the southern economy that the abolition of slaves and the ending of slavery would of course mean a huge economic blow to the south. While the north enjoyed a larger population and a much larger industrial output compared to the south, the south was the richest part of the nation at the start of the war, something to the tune of $3-$4 Billion dollars worth of land and slaves.
The sub-questions here are a bit more difficult to answer and require a more nuanced perspective to address. There were certainty compromises offered and enacted by various administrations prior to the war (the Missouri Compromise, the Kansas-Nebraska Act, etc.), but the idea that the south did or could ever contemplate relinquishing their slaves was never seriously under discussion. Southern political and economic power was so tied to slavery that they would never, under any circumstances, give them up voluntarily, even if they were bought out by the government or through some other economic incentives. Southern politicians increasingly fanned the flames of southern slave holder rights, especially John C. Calhoun, that not only did southerns refuse to ever contemplate giving up their current slaves, but they would refuse to allow the United States government to restrict or prohibit its expansion into new territories and states as they were added to the Union during the early part of the 19th century.
Economists of the day, especially southerners, were certainly aware of the economic and political blow abolition would of course bring to the south. This reality was in the minds of southern politicians when Lincoln was elected, who ran on a compromise platform (compromise from the Republican point of view) in the 1860 election. Lincoln ran on the platform that there was no constitutional or legal basis to attack slavery where it existed currently, but he denied the rights of southerns to force the expansion of slavery into new territories. The result of his election on this platform was a clear sign to the south that the north was determined to place restrictions on, and potentially even abolish, slavery and to them this was unacceptable
There is a very interesting book called Storm Over Texas that very much deals with the politics of slavery of the time, including the economic issues involved. The premise of the book is that the annexation of Texas into the Union was a major, perhaps the biggest, catalyst to the war as it represented a HUGE new territory that southerns were determined to expand slavery into and increasingly made northerners equally determined to oppose the further expansion of slavery.
https://www.amazon.com/Storm-over-Texas-Annexation-Controversy/dp/0195315928