Switching regulator layout advice
General Information and Current Flow

Buck converter has two stages depending on the state of the switch. The switch, in your case, is in the IC and is in between pins 5 and 6. Let's draw the first stage where the switch is ON and D1 is reverse biased. As you can see, the loop is big, because the ground island limits where the current can flow. In order to have a smaller loop, it should have returned right under the yellow trace.

In the other stage, which is not drawn here, things are almost going to be the same, because of the ground island.

Here is a good read on ground bounce.



About Feedback Resistors

Also, here is a very good read on SMPS layout which includes a section in page 14, about laying out feedback resistors. According to it, instead of connecting C6-R1 junction to L1's pin, connect them to C2's pin. This will reduce the amount of extra current that this track will carry.

About the Inductor

Your inductor is fine if it does not saturate at 1.3 A which is stated in the datasheet as below. So, a 1.6 A rated inductor will do fine. Increasing the inductance to 10uH may improve your light load efficiency, but if it brings a higher DC resistance, than you will have lower rated-load efficiency.


  Choose the inductor ripple current to be 30% of the  maximum load
  current. The maximum inductor peak  current is calculated from:
  
  \$ I_{L_{MAX}}=I_{LOAD}+\dfrac{\Delta I_{L}}{2} \$
  
  A 1µH to 10µH inductor with a DC current rating of at least  25%
  percent higher than the maximum load current is  recommended for most
  applications.


What to do?

What I would recommend is to remove that island completely and have a solid unbroken ground plane. Also, adding multiple vias right near every grounded pin, for example right near C2's pin on the right side.

One more thing to say is that your input capacitor C1 may not be enough. I once made a buck converter with a TPS5450 chip which also, in the datasheet, recommended a 10 uF input capacitor. After couple of fried chips, it turned out 10uF was not enough. I would recommend adding 2 more footprints so that you can populate a 22uF and a 100nF, later on, if needed.