What key would give me a note off value?
That depends on the key map you're using. Usually the key next to 1 would give you a note cut, and the one next to 0 a note-off. I'm not 100% sure about non-German keyboards, though, so the best place to look up the keys is on the keyboard settings (http://wiki.openmpt.org/Manual:_Setup/Keyboard) tab - you can use the "Find" field there and enter "note off" or "note cut" to find the keys you are looking for.
Also, please don't hijack the sticky threads for asking questions. The "updated keymaps" thread has nothing to do with your question, and the "VST instruments" topic is a collection of VST plugins, not a place to ask VST-related questions. If you have a question, create your own topic and ask it there.
In Impulse tracker it were the ~ and 1 key to do note off and note cut. If you use that layout, try these keys. 1 = ^^ (note cut) and ~ = ~~ (note off)
But yeah, best thing is to just look it up in the keyboard settings.