Wow, someone actually saw this game! Thanks for your feedback, it was very helpful.
I've fixed the couple problems you've mentioned. I increased the distance the enemies need to be away from the player to spawn and I added a delay for restarting the game, so you don't miss the game over screen.
I've also added the difficulty curve and map loop you mentioned and I think it's way more fun now.
I've really enjoyed making this game; it's been a great learning experience though sometimes the code makes me want to tear my pc to shreds.
