Beautiful panorama. And nice result for an autostitching funtion.
And the good news: the problem is not in the pictures or in the technique of the pictures taken.
At that distance the nodal point is pretty much not an issue. (ever)
The overlapping looks just fine too.
The problem is the "auto" in the function you mentioned.
The problem is the same as if you grap 3 cola botles by the neck. The bottom end will spread out. And that is what happend here. The pictures were autostitched in the upper middle and the lower end of the resulting immage got streched out.
Even when all pictures are fine, autostitching functions tent to bend pictures, depending on what the programm decides on matching together. In bad cases the result looks like 'snakeways'
(in bad cases changing from picture to picture).
The previous post is verry promising though.
good luck !