That's the small building on the triangular space between the Howe Street ramp and the Granville Bridge (see wrenegade's pic of the model below) . The construction on that one is well along now.
Hard to say for certain from the photos but it looks like there is approximately 21 (maybe 22) floors to go.
Yes, that's my guess, too. I'm thinking the final height could be about as high as the cranes in this shot. It's going to be quite prominent as seen from the south.
You can see how they are expanding the floorplate size.
Not every balcony / cube is being reduced - only every second one.
I've marked it in orange below: