The answer is President;Senate
Since the cabinet will be a direct support for the presidents in realizing his/her plan, the president has the right to personally pick the members based on the expertise that the president see fit. In the selection process, the Senate only has the right to give suggestions and to confirm it
Climate should be a good factor
The answer really depends on which of the 13 Southern states you are referring to. Each state issued their own Ordinance of Secession, in either 1860 or 1861. Hope this helps.
Be ready for an attack/ threatening power.
The celebrite that you are looking for is mlk.