Actually, the Emancipation Proclamation freed thousands of Southern slaves.
Regarding "either all slave or all free," here is what Lincoln actually said:
Either the opponents of slavery will arrest the further spread of it, and place it where the public mind shall rest in the belief that it is in the course of ultimate extinction; or its advocates will push it forward, till it shall become lawful in all the States, old as well as new – North as well as South.
You really should read David Donald's books on Lincoln, especially
Lincoln Reconsidered. Lincoln was no tyrant and no radical. Lincoln's lenient, merciful Reconstruction terms enraged the Radical Republicans.
Regarding McClellan, we must understand that because he opposed brutal warfare and was a Democrat, not to mention that he ran against Lincoln in the 1864 election, the Republicans attacked him with vitriolic propaganda, especially the Radical Republicans. The portrayal of McClellan found in most history books is a carbon copy of the Radical Republican attacks on McClellan during and after the war.
Until the 1970s, there were plenty of historians who defended McClellan's record and answered his critics. Starting in the early 2000s, a growing number of historians once again began to challenge the traditional portrayal of McClellan as a dawdling, timid general. One of the best defenses of McClellan is Dr. Ethan Rafuse's 2005 book
McClellan's War. Dr. Rafuse refutes every criticism of McClellan point by point. BTW, Dr. Rafuse is a professor of military history at the U.S. Army Command and General Staff College.
I address every major attack on McClellan in my online article
Answering Some Criticisms of General George B. McClellan. None other than Robert E. Lee said that McClellan "by all odds" was the best Union general he fought against during the war.