Well, since hydrometers are evil, there's no way for you to know if it is done. I've had over-night ferments. Wait the standard week.
The only time you want oxygen in your process is at the beginning of the ferment, more is better.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk