1. Seems to make reasonable sense to me to be honest. If you get an airspeed loss just before V1 for example, by the time you get back to v1 again you are going to be further down the field than you ought to have been at calculation stage.
2. Should normally be using Flap 15, but may need more if field length limited for landing.
3. No idea, but I was always taught to use EGT as a primary indication for determining engine failures on light twins, since it is the most immediate indication when compared with CHTs etc, so maybe a hangover from that?