And yeah I don't get how you guys can't get past those as well XD. Here's a tip: Start off upgrading your first weapon all the way. It's powerful that way and you don't waste money on ammo.
aresius was right... "Build for last campaign: one spread machine gun, one barrier decoy, 4 damage buffers. You'll win with no effort at all."
I took the advice and it worked, literally no effort. Just click and hold on one spot.
 "Fancy Pants Adventure: World 2"){kind=icon}
 "Bunny Invasion 2"){kind=icon}
 "Don't Look Back"){kind=icon}
 "StormWinds: The Lost Campaigns"){kind=icon}