The version I linked in the description fixes some of these issues. Mainly I didn't have time to actually balance the game, I had to just go with the default values I picked which are way unbalanced.
Fuel is gotten by destroying the small abandoned ships, its a drop, but probably gets mixed up with the scrap that is also spawned.
You can also trade scrap for fuel in the pause/map menu. But because the balance is terrible in the first version you can't get enough scrap to make it a usable feature.
The end of space thing, I wanted to add a barrier that made sense with the setting. I was going to try and add like a barrier sprite. Since the player is like a contractor sent to collect scrap they are assigned to a sector, but had no time to implement this so just went with a barrier.