In this chapter, I believe, we are told three things about Dill's father. First, he is taller than their father. Second, he has a pointed black beard. Finally, he is the president of a railroad.
We do not know if any of this is true, but it seems that Jem does not believe the last claim, at least.
To me, this shows that Dill does not really have a very close relationship with his father. He is trying to make up some idealized father. His fantasy father is one who is tall and maybe a bit dangerous looking with an important job. This implies to me that Dill is not satisfied with the way his father is and I assume that is becauses his father does not really pay attention to him.