Just a suggestion:

Can't you eliminate the need of the move icon by using our fingers?
(Our finger is having a bigger radius than stylus) this way you can detect if we want to write/sketch or just moving the page.

Similar can be done to the icons (big transparent icons where you can see through them into your sketch) if we hit them with our finger (Where it have a bigger radius) it will activate it and in same if we just wrote/sketched through our stylus and passed near the icons it will ignore it.

I hope I gave you a clear idea of what I am trying imply here.
&
Good luck in your project

Edit:
The same concept can be done though pressure, you might want to check this out http://wiki.maemo.org/Using_touch_screen_pressure_data