1. Basically it's limitless. (Although it's limited by playability. Too large isn't really fun anymore.

)
2. Jump between stars is the same as jumps between planets.
3. Waiting until your fleet arrives, nothing else.

4. Your wish is an order to me:
A light frigate in front. Behind it some fighters and a capital ship.

The same from above.

Zooming out we see our capital planet and some mines/other structures.

The blue shaded area is a grav well. This is basically the "map" of a planet. In this area your fleet can operate.

Zooming further wee see the whole solar system with two unexplored planets and the star. Ships can move from planet to planet/star to star/planet to star, along those jump lines.

Still zooming we see some neighboring stars. Our planet from before is still shown as a symbol.

Zooming out we see even more neighboring stars.

Even more stars which make it hard to differ between the individual stars.

This game was created with a thousand suns and 5'000 planets.

The light of a thousand suns is nearly unbearable to the naked eye.

A symbolized scout in front of a green star.

Zooming in we almost can't see the scout ship itself.

A little bit nearer.

Still going nearer.

It's a very large star.

A very nicely playable map with one star and a hundred planets.

As you can see, gigantic maps are quite possible, the only thing limiting will be your processing power. And the amount of time you've to spare, of course.

Btw. as a side note. Please Ironclad, change the star system abstraction if zoomed out to something less galaxy like. It makes large maps really ugly when zoomed out alot.