Do the dipole antenna edges have earth potential or is it a closed circuit made of co-axial cable?
A1: It doesn't flow through one direction during the half cycle, it's AC. 

"Normal pole antenna" - what kind is this antenna? Perhaps you meant quarter wavelength antenna?

A2: The current flows through air due to the capacitance, from one half to the another half of the antenna - for a dipole. 

For a quarter length, the ground acts as the second part of the antenna, therefore the coax is grounded at the antenna. A dipole antenna has to use BALUN transformer if fed from coax.