Was the civil war inevitable? How might compromises have forestalled the division between the North and the South? Were economic or political issues at the heart of the conflict?

Usually major historical events are the result of cumulative changes occurring over a long period of time. I don't believe that anything in history has been absolutely inevitable if one goes back to an early enough point before such an accumulation of things has had a chance to start, and then theorizes that if such and such very first things had somehow not happened, then the following chain of events that ultimately led to war would not have occurred either. The only way one can judge historical processes to have been absolutely inevitable is to say, alternatively, that mankind's actions are foreordained, by God or destiny or some unknown mystical force, and that man is therefore not free to choose his own actions, but rather, fated to do only what such a force intends him to do.
With the US Civil War one has to go to a very early starting point and choose an event or series of events that might not have occurred, such as, for example, the invention of the cotton gin. It's common wisdom that the increased speed this enabled in the processing of cotton led to the "need" for more enslaved people to harvest the cotton. Without such a need, it's conceivable that the Southern states could have passed gradual abolition laws as the Northern states did. This is possible, but unlikely in my view. Or, if the ordinance proposing the non-extension of slavery to the southwest territories had been approved, as the Northwest Ordinance was, then slavery could not have been extended as it was to the southern territories not yet organized into states at the time of independence. The much smaller geographic area in which slavery was practiced would then have resulted in a relatively disempowered South, which consequently might not have had the confidence to mount a secession effort leading to war, as actually happened in 1860–61.
One can arrive at additional hypothetical scenarios. However, in the absence of such things actually occurring, it is significant that one compromise after another was tried that only had the effect of delaying rather than preventing the "inevitable." Historians have talked and written ad infinitum about supposedly causative economic and political issues independent of slavery, but none of these were significant enough on their own to precipitate war. Sometimes in history the simplest and most obvious explanation is the correct one. The only major factor at the center of the unresolvable conflict was, in fact, the most obvious one: slavery, and this was the cause of the war.