By 1861, the country was riven and the conversation was about over. The Southern States were collecting their hats and coats and calling for their carriages.
The 1859 John Brown raid, while Lincoln did not endorse it or bemoan Brown's capture and execution (very conspicuous, leading "others" -- including almost the entire New England intellectual establishment -- did, publicly and for the record) had destroyed the last remnants of civil union and fellow-citizenship (as per T.R. Fehrenbach and other historians I've cited in the past). When some people tell other people, "we wish you were in fact dead in the ashes of your houses; you deserve it," the community is finished.
In other words you cannot find proof that Lincoln endorsed slavery.
Lincoln was a masterful politician, especially if as you suggest he forced the south to secede and started a war even before he took the oath of office as president.
Quite a feat by any stretch of the imagination.