Hi AposMus.
Regarding your second question, can you use an integer parameter instead?
Or maybe an indexed string array with two entries, on and off.
I had similar problems problem with boolean parameters and if statements. In the end I went with the integer option.
Edit: Actually I think it works if you assign the value of the Boolean parameter to a local variable first.
Something like:
defineParameter("Play",nil,true)
function onNote(event)
local p=this:getParameter("Play")
if p then postEvent(event) end
end