Sylar did try to pop off Peters head once already. "I can't wat to try that one..."
You are right about the clocks as we saw when he knew Suresh' watch was broken. He also used a similar anaogy to describe Brian Davis, Something along the lines of "You're broken, But I can fix you".
And in regards to Peters ability to leech any number of powers we have seen hints of this already. Foremost when he began to overload when training with Claude - in the street after landing on the Taxi.