also, i think if your script is attached to a decoration it will only trigger if you "use" the decoration with e key. based on what you are describing, you just want your key on top of your modified wallblock? so i think put script into a script file "exactnameovlevel.script" and end the script with
map start
that should start your map with the stuff spawned where you want it spawned at. unless you wanted to spawn the key only as result of using the decoration.
but i am nobody, this is just from what i have done with the software. i am like you, reading translated v1.04 manual and trying to make it work :)