Alright, I found out what caused that the fireballs didn't work: 'FartDart' explosion type in "explosions.xtbl" file. When I removed it, they're working good. But now vomit stun gun isn't working. Also RC Gun isn't making panic. That's because they used 'FartDart' explosion.
EDIT:
Here's the fix, so now fireballs should work properly. I removed 'FartDart' explosion type and the Stun Gun vomit upgrade. I also removed reference to 'FartDart' explosion from RC Gun.
NOTE: I removed that fix since new version has been uploaded to OP.