LM5007: Chip overheating

Since this package has no DAP, the ThetaJA will be large.  This means that it is difficult to get the heat out.

I would try to increase the copper area for the ground and VIN pins to help as a heatsink.  I am not sure what

ambient you need to work with, but anything that will reduce your ambient temperature will also help. 

You may try to run at a lower frequency, to reduce the switching losses.  If you have an auxiliary supply to power VCC

you could try that to help reduce losses.  You might also try swapping the device for another unit; the TSD on the unit you

tried might be too low.

Product ambient could be 40C and possibly a 10C rise above that, although typical operation will be at room temp. What part does the evaluation board use and can this part realistically deliver 500mA or should I be looking at a different part?

The EVM is usually designed for 25C. 

I would use Webench to find a device that meets your requirements.