2. Did the South typically use the phrase "states rights" to describe a perceived right to keep slaves even if the constitution was amended to abolish slavery like the corwin amendment would have done? How did they explain their use of states rights?
the Corwin Amendment to the US Constitution had nothing to do with abolishing slavery. It in fact would have prevented the United States government from interfering with it in any way
within the States... while allowing for its abolition in the federal Territories. The text read:
"No amendment shall be made to the Constitution which will authorize or give to Congress the power to abolish or interfere, within any State, with the domestic institutions thereof, including that of persons held to labor or service by the laws of said State."
Had this Corwin Amendment been ratified by the necessary number of the States, and become a Constitutional amendment, it would have been the 13th Amendment... The actual 13th Amendment, which was ratified shortly after the war in 1865, outlawed slavery in the United States, etc.
The Corwin Amendment first offered to the States of the United States on March 2, 1861 as a possible compromise means of arresting the secession movement; after many of the Southern States had seceded and formed a confederacy. Though notice of it being on the table was shortly sent to the Southern governors by President Lincoln's new administration after his March 4 inauguration, it was ignored in the Southern Confederacy.
Here's a letter Lincoln sent to Governor Perry of Florida in March, 1861:
Lincoln to Perry, 1861, Corwin Amendment...
The South was uninterested in part, because the federal government did not have the delegated power to ban State slavery anyway (outside of war powers), and more, because the principal point in contention in 1860-1861 was not slavery in States, under State laws, but slavery in the Territories of the United States, which were managed by the laws of Congress.
In the pre-war politics and election of 1860, the Republican Party wanted to ban slavery, any legal "property in man" etc., in the western Territories, and Lincoln ran on that platform. The Douglas democrats wanted to extend to the Territorial populations "popular sovereignty" on the issue, and the "Southern" democrats, pressed for the States rights, viz. the "property in man" held under State laws, to be protected and recognized in the federal territories.
Senator James R. Doolittle (Rep., WI), in the Senate, December 4, 1859, speaking to the Southern Senators... who had threatened secession over any curtailment of the carrying of slaves from the States to the Territories...
The Southern democrats favored the "States rights" of slave property, recognized by State laws, being similarly recognized in the Territories of the United States...
Regarding this states rights in the Territories issue, Jefferson Davis, a leading States Rights advocate after Calhoun's death, promoted the threat of secession, should the Southern States be rendered powerless in Congress over the Territories..., as in this 1858 speech in Mississippi:
Later Davis framed the issue of States rights in the Territories as not one of "extending slavery" into the US Territories (which is how the Republican Party viewed it), but akin the right of the States to send it there...
When the Republican Party, which promoted to ban slavery in the Territories, won the Presidential election in 1860, several Southern States seceded and formed the Southern Confederacy... and the war commenced some months later in April, 1861.
There is an anecdote shared by Col. Oates of the 15th Alabama, later Governor of that State, on the score of States' rights in the Territories, regarding Generals Jubal Early and former States rights presidential candidate Breckinridge, now a Confederate general himself, late in the war...
John Will Dyer of the 1st Kentucky Cavalry, CSA, put the issues of 1860, and the States Rights subject, this way in his post-war memoir...
And noted in those later years to his Union veteran countrymen,
3. What are some examples of prominent newspapers, speeches, or writings from Northern men about the change in the war aim as of 1863?
Over a year after the commencement of the war, the US passed a law approved June 19, 1862 banning slavery in all the Territories of the United States. This law reads...
"CHAP. CXI.–An Act to secure Freedom to all Persons within the Territories of the United States.
Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That from and after the passage of this act there shall be neither slavery nor involuntary servitude in any of the Territories of the United States now existing, or which may at any time hereafter be formed or acquired by the United States, otherwise than in punishment of crimes whereof the party shall have been duly convicted.
APPROVED, June 19, 1862."
Shortly after was passed the "Confiscation act" of 1862, which included the alienation of property, including slaves, by persons in States found in insurrection or rebellion against the US...
General McClellan, who supported a war for the Union, was opposed to these measures. As noted in the Democrat Party National Committee proceedings of 1864 which nominated him for President..., he had remonstrated against them in 1862 while still commanding the Union army...
....and shortly after came the "Emancipation Proclamation" of President Lincoln, under his war powers, effective from January 1, 1863 affecting the Confederate States...
Emancipation Proclamation Text, National Archives.
On the subject, Lincoln had written Horace Greely in September, 1862 regarding the measure, that so far as he was concerned, it was inextricably intertwined with the Union cause:
November, 1863, President Lincoln's Gettysburg Address noted a "new birth of freedom..." relative to the Union victory...
"But, in a larger sense, we can not dedicate -- we can not consecrate -- we can not hallow -- this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us -- that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion -- that we here highly resolve that these dead shall not have died in vain -- that this nation, under God, shall
have a new birth of freedom -- and that government of the people, by the people, for the people, shall not perish from the earth."
In 1864, running against McClellan, President Lincoln headed the "National Union Party" and chose Andrew Johnson, formerly a Democrat from Tennessee, and lately the pro-Union military governor of that State, as his VP...
National Union Party Convention, 1864: Google books
Andrew Johnson, by April, 1863, had advocated the Emancipation Proclamation to the Union men in Tennessee, and the crushing out slavery...
The opposing Democrat party in '64 remained critical of President Lincoln's administration, and handling of the war, etc. Speech of Governor Parker of New Jersey, Aug. 20, 1864, claiming Lincoln's administration had forced the South to abide the Confederacy in a measure by its abolition war measures...
Handbook of the Democracy, '63-'64: Google books
Lincoln was handily reelected in November, 1864.
Bringing the