I know this may sound extreme but dont you like to inform the police? there is now a way of informing them and requesting them to keep your details annoymous...
If the management & the security cant provide the people in the compund proper safety then you have to go to someone who can...
Cant you maid be on the look out to see who sticks notes ? if like you say he knows when your maid removes them then he lives rather close to yr home.