Roger, I made a model myself of the first bullet using James camera footage. Here it is: 1; 2; 3; 4; 5; 6
I’m not questioning your model, but I think the Google Earth input height are not accurate enough.
I will try to explain this without using any calculation. If your height of the shooter from the vent (6 feet below the top of the roof) is correct, then it almost at the same line of sight of Trumps ears in the photo on the left, therefore the bullet (disregarding the ballistics) would come at the same height of James camera eyepiece and that is way above the rail.
Therefore, the height of Google earth is not accurate enough. One feet of error in Trumps elevation will result in 6 foot deviation on the South side of the building position, one foot is within the margin of error.