That just shows you the respect the networks had for the AFL at the time.
Yes it does. I think after that game the networks changed their policy and now they always keep NFL football on the air until the end of the scheduled game in each region. They switch to other games if the scheduled game isn't close, but they stay with football in case there's a sudden dramatic comeback.
But NBC was the monopoly carrier of AFL games. If they didn't carry the AFL they would not have had any pro football.