Finally got the circuit working as intended.

The difficulty was primarily due to layout considerations (improper ground pours + ground loops) and having a bulk electrolytic on output.  With 3x 10uf ceramics it is working great! 

I used a 3A 2.2uH inductor which is not exactly to spec so I'm getting ~1.5A output, but that's more than I need anyway.  I think the reason the datasheet calls for such an enormous inductor (>6A Isat!) is due to low impedance windings.  This is needed to achieve the ultra-high efficiency (I think).  The datahseet recommends an incredible 9.7mohm with an Isat off 11A! This is shocking for a DC-DC that only pushes 2A / 5W of power...

The substitute I found (their recommended one is obsolete) is here:

https://www.mouser.com/ProductDetail/Bourns/SRN6045TA-1R5Y/?qs=sGAEpiMZZMsg%252by3WlYCkU3tyM9HcjVri8VL%2fIY%252bgGEQ%3d

This has slightly higher resistance but I think will do the job well.  Right now with my successful layout I am getting 70-85% efficiency.  Let's see if this part bumps that up higher...

Also, I am going to expose the ground copper beneath the ship for better thermal dissipation.  Not that it needs it, it didn't break a sweat running for hours at 1.45A.  It's good practice though.