1. RTO at V1 doesn't mean you will stop on the runway, plus what CB said above.
2. As CB said. It may also be there for engineering as well.
3. N1, N2, FF, Oil QTY, EGT are indicators to determine the status of an engine. EGT indication usually just backs up what the other indicators are saying. So it's not so important having the indication for diagnoses purposes.