1.you can fill DS156 even in the consulate U.S. Calgary. There are two desktops and one printer there. I saw somebody busy filling the form there. I finished this form one day before my appointment.. H( a8 b, ^6 {1 m1 R9 J$ e. D4 ~
2. I don't have experience in your situation. However, I did not see any rejection in Calgary that day I was interviewed. Because everyone was asked to give them a X PRESS envelope. Nobody had the passport returned the same day (that means rejection). More than 120 people were interviewed that morning.