Delete gamemode_zombie form your add-ons folder, it still effects the game when disabled.
Trees are hard to destroy, there could be an admin wand that can effectively destroy extremely high HP stuff.
Yes being overburdened and then lessing the burden will not turn you back, you must Ctrl K in order to reset back.
When you change from a white to black, it'll work. But it won't work when changing black to white unless you reset and then do it.