We agree. Lincoln felt that slavery would die out if isolated. Looking at the economics of slavery, I think he was correct but IMHO, the 'death rattle' of slavery could possibly have been even more horrific in terms of loss of life than the Civil War. Think of Santo Domingo.
Part of his aura is as a geat emancipator which is not what he really was.
Disagree. If it had been in his power to end slavery early in the war, he would have. But that was not a political possibility. As late as the summer of 1864, many Republicans were urging him to retract the EP. To his everlasting credit, he refused even when it looked like he would lose the election. Sherman and Atlanta changed the political dynamic, and it became perfectly clear that the war would end only through victory there was no need to attempt to appease the slave power. It also became more clear to the general population that Lincoln's words from years before were indeed true --- "A nation can not endure half slave and half free. People understood that the regionalism was caused by slavery and they were then willing to see it ended. When the people allowed, Lincoln immediately began pushing the 13th Amendment which was passed by both houses in a matter of months.
His greatness would lie in recognizing the overriding necessity of saving the union ( if it meant dragging the south back )
We agree. He focused on first things first and never allowed himself to get too far beyond public opinion. (Read Frederick Douglass' dedication speech at the Freedmen's monument in Washington.)
The other aspect is it was easy for some in the North to moralize over slavery when their economic well being was not affected...
Generally true, but I think you overemphasize the amount of "moralizing" in the North over slavery. The radical abolitionists generally were not moralizing, they were operating from religious conviction and were as ready to destroy the Union to destroy slavery as the secessionists were to destroy the Union to preserve slavery. The great bulk of the north came to understand that slavery was the cause of the war and it needed to end to allow the Union to be resumed.
as there were plenty of immigrants and child labor to staff the factories etc
Rationalization. For 4 million blacks in the south, hard labor began at age 6 or earlier. Immigrants came to America for the opportunity to work. They could have as easily gone to the south as the north but because of slavery they were neither needed nor welcome there. Slavery kept the south backward and kept most white southerners poor.