My first three games I thought it was pretty tough, I didn't like being dropped into a difficult new level, dying and being sent back to the start.
But on my fourth game, I completed it!
My strategy was to pick up more crew members from the distress beacons. When I was low on crew or on resources, I would go back and play an earlier level planet.
I surrounded my ship with strong turrets, and kept one character repairing them. My crew couldn't fight very well, so they just had to hide and sneak past enemy lines.