Then book from Nizamuddin only.
Although Waiting List is quite high considering 1A. Date is far, almost 2 months. Can be tried. But do keep a backup option in 2A just in case.
Even I couldn't travel in 1A this time in Diwali Rajdhani Trips due to this. Even when I booked at 4th July for 21st October Traveling. Had to travel in 2A.