The fast track line is often slower than the regular line.

At 10:00 to 11:00 and after 22:00 there is a long queue and the fast track counter is staffed with only one person, no matter how many people queue up.

You don't need the fast track card. A business class boarding pass or *Gold card will be sufficient.

Asking a taxi to drive you to Sultanahmet will most certainly double the price. Ask the taxi driver before you leave about the price. I live in Beyoglu and my taxi passes the Sultanahmet area. Usually I pay 45-55 Lira, depending on the traffic. So Sultanahmet should be maximum 55 Lira.