I figure it's better to forge forward and retcon if necessary than to get stuck in the weeds.
I'll start moving forward with an alt-Wo1812 where New Orleans isn't captured; I can explore how things would be different if New Orleans is captured after.
The immediate impact of the War was a severe disruption of the economy of the Floridas, which had been in full cotton boom.
Thousands of Creek refugees and their slaves are forced out of Georgia and OTL northern Alabama into West Florida, while during and after the War many pro-American settlers in the Floridas would move to the USA.
As in Canada, after 1815, the Floridas ban immigration from the USA for several decades in an attempt to keep the area under British control.
At first, the American economy had actually suffered more (due to the effects of the successful naval blockade on foreign trade), and had a harder time bouncing back...the USA would stay in recession until about 1821.
The slow recovery of the USA's cotton exporting in fact helps Florida's recovery. During this period, as burned cities are rebuilt and forts upgraded, Florida begins to evolve into a wealthy, developed colony.
And progress is being made, albeit slowly, toward abolition. In 1822, it became illegal in the Mississippi Territory to kill your own slave without good reason (which, believe it or not, counts as "progress").
In 1824, although public slave auctions were already rare in the British West Indies, they became illegal, as did splitting up families and couples by selling one of them.
These must be seen as very minor impositions on the owners to have some semblance of human dignity, but to some of the planters, it is seen as a constraint on the exercise of their capital. (Restrictions on their sale lead to a reduction in their value, meaning wealthy slave owners would have a financial incentive to move to the USA, where their slaves are worth more, because they have fewer restrictions governing their sale and treatment).
From around this time, the Planters who most enthusiastically support slavery are more likely than the population as a whole to move north into the USA. The phenomenon of course is most noted after the Act Abolishing Slavery in 1833, but it began at least a decade earlier.
Prior to these double effects - the banning of American immigration and the improvement of the conditions of slaves in the Floridas - there would be little to no discernible difference in the racial attitudes of white Floridians compared to their American brethren in Georgia, Charleston, or Mississippi.
This would begin to change, every so slowly, after the war.
Slavery in the West Indies, however, was no benevolent institution, and slave revolts would have been just as frequent and bloody in the Floridas as elsewhere.
As happened in many West Indian colonies and American states, Free people of colour may lose their rights of citizenship (or have them restricted) in the years leading up to the War of 1812 as the plantation economy is expanding.
In 1831, perhaps in response to a wave of violent slave rebellions in the West Indies, the British Parliament passed a law which guaranteed free people of colour the same rights of citizenship (with the same property qualifications) as free white citizens.
Due to undemocratic nature of the colonies and the property qualifications for voting, this didnt mean a substantial increase in the political power of free blacks at first - but it did put them on a sound legal footing they had lacked before. They were citizens, and they were allowed to live in Florida.
Of course, this gave some extra punch to the Act Abolishing Slavery.
Passed in 1833, the provisions of the act were that beginning on January 1st 1834, all slaves in the British West Indies, British North America and Cape Colony would become indentured servants - with an indenture of six years, ending 1840. During this time they would not be paid, but would be limited to 9 hours of work per day, six days per week.
Slaveowners were entitled to compensation. The amount per slave was approximately 20 pounds (although this varied quite substantially, depending, it seemed, on how well liked one was by the Crown).
This was deliberately set significantly lower than the market value to avoid smuggling and "breeding" for profit.
Another stipulation was that, to get your compensation, a slave owner had to travel to London.
(It should be noted that compensation paid to the slaves was never considered).
Because of the cost of a trip to London, this meant that only the wealthiest planters could realistically travel to London to get their funds.
Since emancipation had also changed the nature of their livelihood or stood to shortly - the former slaveowners were in fact just as likely to sell their properties in Florida and stay in England or move on to some other location with their compensation.
There was also, as previously mentioned, a strong incentive to move with your slaves to the USA.
In East Florida, a smaller percentage of whites are slaveowners, and therefore the numbers of those who leave are smaller proportionally.
In West Florida, a higher percentage of the white population were slaveowners, and therefore a higher percentage leave - the planters being disproportionately Anglo, this has the effect of slowing French language attrition in West Florida.
There were of course those who would take their compensation and use it to try to start new business ventures in Florida - other types of plantation or even railway and canal building.
As the "apprenticeship" period was winding down, absenteeism increased. This wasnt much of a problem, because the sale of planters' property had itself induced somewhat of a downturn in the economy, reducing demand for apprentice labour.
By the time the period ended, and the freedmen were able to walk off the plantations for good, a glut in the global supply of cotton had already resulted in a severe depression in the USA cotton belt, which would last into the early 1840s.
At this time, many of the freed slaves left the towns and plantations to join the already established freedmen's villages which had dotted the interior for decades.
And, as word spread in the southern states about the freedom on offer in the Floridas, a high stakes game developed between southern militias, intent on securing the border and preventing any slaves from escaping, and the slaves, who, increasingly throughout the 1840s and 1850s would risk everything to make it to liberty in Florida.