Buck converter analysis
Is the LED two or three terminal? You have both a red and green arrow indicating the light output, and it would make sense if the green side of a bicolor LED were connected from R2 to ground, and the red from R1 to R2, then the LED indication would change from red to green if the fuse blew.
  Resistors are available as fusible type, which will fail predictably under overload conditions to an open state.

C1 and C2 are likely split into two for either or both packaging reasons compared to a single larger cap, and because the ESR and inductance of the two is likely better than a single one, so it'll be more effective at dealing with the ripple.
  That's the reasoning behind C6 too - the smaller cap has a lower inductance, so will be effective at higher frequencies where the larger one is beginning to be less so. 
  C5/C6 and L2 form a pi filter to reduce the noise presented at the output.

The variable resistor is part of the feedback to allow the output voltage to be tuned, section 9.2.2 of the datasheet explains this.