At 1.012, the beer should not taste sweet. Many great beers finish at 1.010-1.012. The layer on the bottom of the fermenter isn't sugar- it's trub. That is spent yeast, proteins from the wort, hops debris, etc, that all fall to the bottom. If the SG is still 1.012 two days after the first reading, it's safe to bottle as it would be done.
Carbonation changes the flavor of sweetness in beer as carbonic acid counteracts the perceived sweetness, so the beer once carbed up won't taste nearly as sweet.
Broken Leg Brewery
Giving beer a leg to stand on since 2006