The 500 ohms are just in the input line to the IC, not in the way of the high current path, so considering the IC consumes less than 3mA that should be inconsequential.
I have done a few different tests shifting the components around, resulting in 3 successful configurations.
Having either the resistor or the TVS on its own is enough to protect the IC, as is having the TVS before the resistor. What seems to destroy the MOS is having the TVS next to the IC's Vin pin while having the resistor in the way.
I've done controlled load steps with the layouts that worked, not with the one that doesn't, and I have some waveforms measured but nothing worth sharing on the one that fails. I'm guessing that somehow, having the TVS after the resistor makes it harder for the MOS to shutdown.
TVS: SMAJ48CA, just for testing the positive side, I'd move to a more appropriate one once I knew that a TVS was able to keep the IC safe.
Edit: The board so far worked best with a 100 Ohm resistor to protect the Vin pin and the bidirectional input TVS. Attempting to add a separate TVS to ensure VGS didn't burn the MOS was unfruitful. I also increased the inrush cap and added the hotswap cap, in hopes it made a difference.