Hi,
For the spacing on the pendants I'll refer you here just to ease my typing a bit http://www.forteelectric.com/PendantLayout.html as for the light over the sink I had a similar situation and what I did in that case was move the pendant over the sink higher than the outer two. It worked out nicely and the customer loved it. You can see the photos of that here http://www.forteelectric.com/photo4.html Let me know if you have any other questions.
Paul