Found a glitch to help with those stuck on the last boss: Is you pause the game while he's doing his tendril attack the attack animation will finish while the game is paused. You can do this to avoid getting hit.
"And now over to Mark with the news" "Thank you Lisa. Today a home was robbed. The robber managed to steal 200$ from the home 36 seconds faster than the average robber. He also picked 4 locks. Overall id give him about 350 points with a 5 star rating. Back to you Lisa"
A single drone wont do much good unlike a turret or mine, you need several of them to efficently use them to absorb damage but by the time you've ammased enough drones to properly defend yourself the prices for the other towers will be much higher.