3) Lincoln didn't do it to secure black support, but because the attitude of the public had shifted. The shock of so much bloodshed gave the people the need for a moral crusade, and the lack of victories coupled with the death toll was viewed by many as a judgement from God. The draw at Antietam, which the North declared a victory, was viewed as the perfect timing to officially change the tone of the war effort.
4) Completely wrong. If not for slavery, the Southern economy would have been organized in a very different way. Pretending that under these circumstances that it still would wind up seceeding, and assuming that it organized its economy under a strong, diversified, industrial-based system, the North would have had a MUCH less likely chance of winning the war.