Pre Crisis Superman can travel trillions of miles in an instant.
Uh... not seeing how she would be able to? Divination?
Actually as we see SS4 Goku is more powerful than Black Star Shenron (His own power actually reverses Black Star Shenron's actual magical affliction of reducing Goku's age, reverting him to a child state. It was stated it'd require another wish from Black Star Shenron to permanently reverse it... and his SS4 actually reverts it temporarily as per the obscene power being channeled in that form), and that we know the Dragons' strengths/powers correlate with the strength of their creators (The Nameless Namek was obscenely powerful), the combination of Shenron, Black Star Shenron, and Porunga still isn't enough for the likes of Pre Crisis Superman
The Dragons could, sure... if anyone actually gets the idea to do so despite the villains' presence. Frieza? He's gonna hop on the dragons. There's going to be infighting, and Superman could easily end this instantly if he so desired. Given the state of the DBZ characters in one place, Asgard, and Superman's tendency to go to the extreme, likely he will do so.