Did either side really want a war? I honestly don't know. I think that Lincoln was trying to do whatever he could to avoid one while at the same time hanging on to the remaining federal property in the South. But did he really, honestly believe that there could be a peaceful resolution? I don't know for sure. I think that the South was a little more anxious to resort to war believing, as you pointed out, that it would be a short and fairly bloodless one. But once the die had been cast at Charleston there was no more desire on the North to rein in the dogs of war than there was in Richmond.
I like Lincoln. Thought he was a good tough politician. Because I admire his politicial skills, I do not tie myself up in the knots you do trying to justify what he did at Ft. Sumter. You can't have it both ways. He can't be the smart politician he was and be surprised at what happened at Sumter. The two don't mesh. Tey don't have too. We really don't have a dog in this fight so we can be honest about all the players.
He pushed the South, and the South back.