I would NOT stir, slosh or otherwise agitate and it's common for extract beers to be finished at 1.020. You definitely don't want to aerate this!
Since this is a steam beer, you may notice a bit of fruitiness. If you ever want to do a lager-like beer again in the future, you may get better results with a clean well attenuating ale yeast rather than a lager yeast at room temperatures. I've had good results with nottingham at 60 degrees- it was very lager-like!