- The schematic is a little odd in that VIN- is above VIN+. We'd normally keep positive to the top of the schematic.
- What is D1 for? D2 already provides reverse polarity protection.
- There doesn't seem to be any connection between U1's GND connection and the output supply on the schematic although both seem to be connected to the ground plane on the PCB.
- Many of your component ground plane vias are hidden unnecessarily. There is plenty of space in many instances to leave them visible and obvious which would help debug or repair unless you're doing it for heatsinking.
What I see as problematic: -
If you look at the circuit in the data sheet you'll see that the minimum operating voltage for 12 volts out is 15 volts in. You have said this: -
Tried to copy the demo board version, 15-100Vin - 12Vout@1A.
But, you have significantly reduced the input voltage by two diode drops (purple box). I think this will give you problems when the input supply is below 16 volts.
The 2nd issue is your UVLO resistor divider in the red box above. You have set this to disable the chip when the input voltage is below 6 volts and this is waaaay to low. Your circuit, if the data sheet diagram is to be believed, will not reliably work when the input voltage falls below about 16.4 volts (two diode drops above 15 volts) so your UVLO potential divider is missing the point by a long way.
Remember, this is a buck convertor and the input voltage needs to be above the output voltage by some few volts for this chip to work reliably. You also need to sort out a discrepancy on your 0 volts because your input 0 volts isn't connected to your output 0 volts.
I also fail to see why you have an output fuse AND an input fuse. You should only need one.
I don't see there's any point checking the layout on this basis.