I like the sound of your reward system. DD loves things like stickers balloons etc. So that might be a great way to get over this hurdle.

Hopfully it is just an age thing. I mean they warn you about the terrible 2's(which is what i am currently going through with DS, so double trouble for me right now!), but they never tell you it gets worse at 3 cause they know which buttons to push and at 4 when they know how to interacte more and know exactly what gets you mad etc. I am so so glad DS can't talk yet!