Power supply protection
Use Nexperia PESD1CAN for transient over voltage event:
https://www.nexperia.com/products/esd-protection-tvs-filtering-and-signal-conditioning/automotive-esd-protection-and-tvs/lin-can-fd-flexray/PESD1CAN.html
They are excellent and I successfully tested them with an EFT tester.
They are automotive qualified and cost nothing.

For reverse polarity use diode S1M

For under voltage use a lot of capacitors on the regulated output of your regulator

Order:
PESD1CAN TVS comes first and then the S1M diode.
If you switch them, the diode will blow at the first over voltage event.