Can someone please be so kind to answer these three questions? Id be truly grateful!!

1) Why is the value of the hydrostatic pressure 0 kPa at the heart level instead of being 0 kPa at the top of the head? What are the physiological reasons for that?
2) Why is the venous system so important when talking about the impact of the hydrostatic pressure on the circulation?
3) How does the blood go through the foot capillary system (of a standing person!) if the pressure at the venous end is 12 kPa, and at the arterial end only 4 kPa?

Thank you all very very much
And, btw, I sincerely apologize for any grammar mistakes made Im a foreign and still studying English.

Thanks again!