It may be
Although I am not totally convinced by all my explanations and will continue to think, here they are:
I'm pretty sure this one may be difficult.
Maybe linked to the saying 'to defy gravity' i.e. something is difficult
I am the ruler of the clouds in the sky.
gravity controls the clouds by balancing the upward force and pulling water vapour together
The cause of their fall, when the clouds cry.
gravity causes water moisture to fall when it gets too heavy
I am the forces of many things unseen,
everything, even unseen things, enact a force of gravity
Two people have a tiff, and I’m in between.
Gravity acts between any two objects (or in this case people)
The real reason for almost everything you do.
the 'gravity of the situation' means the importantness of it; could be the cause of everything you do
The imaginary eyes of people staring at you.
really not sure about this one
I am a force with which to be reckoned.
gravity has the power to control planets; galaxies and everything in our universe
I’m everywhere with each passing second.
gravity is always acting; no matter how far from an object you are