"Even in 1811, that news would have been in Virgina in a week, if not less."
This might have been true in 1831, but not in 1811. News of the Treaty of Ghent (Dec. 24, 1814) didn't reach the Gulf Coast until Feb. 13, 1815. The Battles of New Orleans (Jan. 8, 1815) and Fort Boyer (Feb. 11, 1815) occurred in the meantime.
We should also be aware that none of the states along the Gulf of Mexico existed prior to 1812. Communication with the eastern seaboard states took place via the Mississippi River or the Natchez Trace or the port of New Orleans. The uncertainty of mail service and newpapers, in their infancy west of the southern Appalachians at that time, cannot be discounted.
"Again the decade where attitudes changed. The free black population [of Alabama] doubled from 1820 and was on its way to being a large population."
The 1830s was indeed a decade of change. In 1832 the Nat Turner Rebellion prompted the Alabama state legislature to change the law so that free persons of color had to leave the state. You properly noted the impact of this law, sharply reducing the rate of increase for free persons of color. The slave rebellion prompted another state law which forbade importation of slaves into Alabama. See J. Mills Thornton, Power and Politics in a Slave Society: Alabama, 1800-1860, (1976) p. 319, and my prior post on the Code of Alabama for 1852.
In 1830 no less than eight societies for the emancipation of slaves existed in Alabama. Guess how many there were in 1860?
Aside from the Nat Turner Rebellion, the other development which hardened Southern attitudes towards slavery was William Lloyd Garrison's abolitionist newspaper, "The Liberator", which began publication in 1831.
I failed to note an exception for the requirement that manumitted slaves leave the state. Exceptions could be and were granted by special acts of the Alabama state legislature. By this means former slaves like Horace King were permitted to remain within the state --