Thanks for your answer TIG, using non modifier keys is indeed a bad idea inside a tool, because they are already bound to lots of different tools. I also discovered that the int values corresponding to keystroke can be accesed like this valueFor_W_Key = ?W a bit weird, but it works. I ended up not using keys

Unfortunately there is no control over the amount of lens shift in SketchUp. There is currently just 2pt perspective - as mentioned, not even that can be controlled reliably.