Shame on you, Organ,.... The green line in your lying presentation extends further back on Houston than Tom Dillard's position at the time he snapped his photo and clearly Dillard's photos reveal a much more acute angle than you've attempted to present as an accurate depiction....
You're doing apples and oranges. Dillard's photo and the "Houston Street sidewalk" 3D view I posted were taken from two different locations. I never implied a replication of the Dillard photo.
Dillard would be so beneath the window that a line projecting from Box A to the President at Z313 would angle upwards relative to the east-west lines of the facade. As the trajectory slope descends, Dillard would have to change his viewpoint to follow it. The slope would be below his line of sight where the shot struck.