Don't let the negative comments outweigh the good! Remember that people are more likely to complain than praise AND it takes 7 positive comments to balance out a single negative one psychologically. Which can make development tough, but you all are doing great.
Also remember that balancing for these games is both key and VERY difficult. This is why big titles often soft launch for months (even years) to tweak such things (and also tweak the F2P stuff).
And now that you have a game engine you an build on it for future games. Don't be afraid to charge again for a future ver 2 of the game (after a reasonable amount of time and updates on ver 1 of course
I've enjoyed the game myself. And while there are some polish issues at times, there are moments of epic space battles that are just so cool. And that's why I keep playing.
