When Sam calls Dean on the phone, Dean immediately drops the phone. When it lands on the ground, the call time is listed as 13 seconds, even though only a couple of seconds have passed.
Near the end, Jo's ghost fills the room with gas to kill Dean. She then causes the windows to break so that enough wind enters the room to break the line of salt. That much air at that pressure would also have cleared much of the gas from the room, likely ruining her plan. Jo would have been intelligent enough to either let the gas itself kill Dean or ignite it from the stove.
This episode takes place in Michigan. Michigan has never had the death penalty and was the first state to ban it via state constitution in 1836. One of the victims, Warren, was originally sentenced in 1981 and eventually released from jail. His death sentence occurred when he was tried by Osiris.
It's established that a guilty person's executioner is determined by what they feel guilty about. By that rationale, Dean's executioner should have been Amy. Except that he didn't feel guilty about killing Amy, because she had killed humans and therefore needed to be 'put down', in his mind. He merely felt guilty about lying to Sam about it. It's not nearly as big a thing to feel guilty about as believing that you are the cause of a good person's death, even if indirectly.
Before Dean leaves for the bar to continue the investigation, you see a Canada Post truck in the background behind Sam. The show is purported to take place in the United States.