You are very right about the balancing. I had a rather hard time figuring out what would be too good and what would be too weak even with having friends playtest the game. In the end I shipped it with some changes to some values and hoped it would be at least decently balanced. I'm really happy to see you've enjoyed playing though! You guy's game is truly amazing btw, I just played it lol
Ps. there's a surprise at wave 20 and an endless mode after that for if you'd ever revisit