the wrench is pretty much non existent after leveling up.. the zombie statues and notes aren't on the map and the stats aren't detailed (how many zombies kicked off the roof, how many notes, statues obtained, etc) Techland made some rookie mistakes.
Some of this is wrong. Zombie Statues, Flags, Notes, Battle Journals, and Voice Mails can all be checked by pressing Square/X on the Inventory menu screen.
The Zombie Statues and Flags aren't shown on the map, because they're just "bonus" collectables. They don't count towards the Achievement/Trophy or Completion %, so who cares? They are there only for the most diehard of obsessive compulsive types.
Finding all of the Notes, Battle Journals, and Voice Mails is REALLY easy with a guide. If you find a guide that does them in a nice order, they're actually really close to each other and it doesn't take long at all.
You can get a Wrench necessary for the Trophy just by joining a low-level multiplayer room from the matchmaking browser. Or New Game+, of course.
The best way to get the Trophy for kicking zombies off cliffs (even if the stat isn't tracked), is to go to the Infamy Bridge when you are very high leveled and just kick them off the edge, where there isn't any water.