A well-detailed summary.
but the couloir is nowhere close to 55 degrees steep, imho. Unless you found some unusual conditions, I would say the top is maybe 35 degrees.
Edit: I went up the right fork, not left. I guess you went up the left so I can't comment on the steepness of that one.
The last 100 ft was 55 degrees when we did it; I measured the slope with the inclinometer on my Suunto; I don't normally check the slope; however, this was considerably steeper than anything else that I've attempted. It was probably quite dangerous at the time because of the wind loading; the right couloir was completely corniced as you can see in the pictures. The rest of the climb was relatively low angle < 30 degrees, in the ballpark of Dana Couloir.
as i said above, i noticed to late that you were referring to left fork... apologies, i can't comment on the left fork