Does he have pets? Nothing gets somebodys attention like messing with their extended family members. The nice thing about pets are, when you damage them, they cant talk.
If he's got a cat or a dog, lop off an ear, bob the tail or poke out an eye, doesnt matter really, just make sure the animal is obviously damaged and still alive. Drop buy the landlords and mention the animal. "Hey bob, hows that cat?"
If you get kicked out, crawl up into the attic and see if you can drop things inbetween walls, some places you can drop food and roadkill behind the walls. Easy to drop in, hard as hell to get out, and the house will stink of rotten foulness.