The Force is more than just a telekinetic ability, it's a state of being that allows them to tap into the energy of the universe, to know a great tragedy has occurred, like Alderaan, or that someone you know is near, to see outside your own perceptions of time & existence
Well, rather, the Force is the energy of the universe, or rather, the energy field that binds all living things in the universe. Force-sensitivity is the ability to tap into the Force and interact with it, whether to perceive things through it or to manipulate objects and minds through it.
As to the "long time ago" preamble. It's perfectly ambiguous. It sufficiently removes the events from the viewers' base of reference, such that no preconceptions can burden it, but also leaves open the potential of still being relevant & connected. Why use the word galaxy otherwise? To give the suggestion that we all may still inhabit the same universe.
That's kind of overthinking it. Like I said, SW is basically a fairy tale dressed up with sci-fi trappings. They took "Once upon a time in a land far, far away," and substituted "galaxy" for "land" because most people are aware of the word "galaxy" meaning some kind of large region in space.
Incidentally, I'm of the rather fantastic opinion that E.T, himself is a user of the force, & potentially a Jedi in his own right. Displays telekinesis, has empathic powers shared with Elliot, & recognizes Yoda, from a child's costume (at least one could interpret it that way) kind of makes you wonder if Jedi can heal like E.T. too. lol
I just read on Cracked.com about a fan theory that E.T. is a Sith Lord, because he has the power of resurrection, which is something only the Sith ever mastered.