TDC = top dead center = 0* before TDC = second from the left.

15* BTDC = base/idle timing on a DET = second from the right. = use a timing gun.

The CAS thing you just have to do. Align the dot on the right. When you push it in, the gear will spin that shaft, because it's helically cut. Once it's in, the left will line up, and the assembly should be near the middle of the adjustment.

Yes, Pins = chain link pins.