Yes, the intention was to stop it from spreading and figure out a way to phase it out over time, not to end it all at once. Nobody had any idea how to end it all at once without major turmoil.

Just freeing slaves all at once would be the mother of all "regulatory takings" in todays terms.

The language he was using was meant to appease the slave states and stop them from revolting.

He kept insisting that because slavery was the biggest issue for the confederate states as indicated by their declarations of secession. He was trying to keep the union together without a long an bloody fight and letting the south keep their slaves was the only way that was possible.

But it didn't work and total war ensued.

The war forced his hand.

Quite right. The war was started by people wanting to preserve slavery.